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<section id="tutorial">
<h1>Tutorial<a class="headerlink" href="#tutorial" title="Link to this heading">#</a></h1>
<figure class="align-default">
<img alt="_images/example_tutorial.png" src="_images/example_tutorial.png" />
</figure>
<p>This tutorial will help you create your first Edifice app.
We will create an app that converts measurements in different units.</p>
<p>First, install Qt and Edifice.</p>
<div class="literal-block-wrapper docutils container" id="id1">
<div class="code-block-caption"><span class="caption-text">Installation from <a class="reference external" href="https://pypi.org/project/pyedifice/">pypi.org/project/pyedifice</a></span><a class="headerlink" href="#id1" title="Link to this code">#</a></div>
<div class="highlight-shell notranslate"><div class="highlight"><pre><span></span>pip<span class="w"> </span>install<span class="w"> </span>PySide6-Essentials
pip<span class="w"> </span>install<span class="w"> </span>pyedifice
</pre></div>
</div>
</div>
<div class="admonition note">
<p class="admonition-title">Note</p>
<p>Edifice supports both the PySide6 library and the PyQt6 library
for Qt bindings.</p>
<p>Edifice prefers the PySide6 library but both are supported.</p>
<p>If you would prefer to use the PyQt6 library and do not wish to
install PySide6, you can run:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">pip</span> <span class="n">install</span> <span class="n">PyQt6</span>
<span class="n">pip</span> <span class="n">install</span> <span class="n">pyedifice</span>
</pre></div>
</div>
<p>You can switch to using PyQt6 by setting the <code class="code docutils literal notranslate"><span class="pre">EDIFICE_QT_VERSION</span></code> environment variable to <code class="code docutils literal notranslate"><span class="pre">PyQt6</span></code>:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="n">export</span> <span class="n">EDIFICE_QT_VERSION</span><span class="o">=</span><span class="n">PyQt6</span>
</pre></div>
</div>
</div>
<p>Let’s create the basic skeleton of our UI.
Copy this code into a new file, <code class="code docutils literal notranslate"><span class="pre">tutorial.py</span></code></p>
<div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="kn">from</span> <span class="nn">edifice</span> <span class="kn">import</span> <span class="n">App</span><span class="p">,</span> <span class="n">Label</span><span class="p">,</span> <span class="n">TextInput</span><span class="p">,</span> <span class="n">HBoxView</span><span class="p">,</span> <span class="n">Window</span><span class="p">,</span> <span class="n">component</span>
<span class="nd">@component</span>
<span class="k">def</span> <span class="nf">MyApp</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="k">with</span> <span class="n">Window</span><span class="p">():</span> <span class="c1"># Top of every App must be a Window</span>
<span class="k">with</span> <span class="n">HBoxView</span><span class="p">():</span>
<span class="n">Label</span><span class="p">(</span><span class="s2">"Measurement in meters:"</span><span class="p">)</span>
<span class="n">TextInput</span><span class="p">(</span><span class="s2">""</span><span class="p">)</span>
<span class="n">Label</span><span class="p">(</span><span class="s2">"Measurement in feet:"</span><span class="p">)</span>
<span class="k">if</span> <span class="vm">__name__</span> <span class="o">==</span> <span class="s2">"__main__"</span><span class="p">:</span>
<span class="n">App</span><span class="p">(</span><span class="n">MyApp</span><span class="p">())</span><span class="o">.</span><span class="n">start</span><span class="p">()</span>
</pre></div>
</div>
<p>Run this code with</p>
<div class="highlight-shell notranslate"><div class="highlight"><pre><span></span>python<span class="w"> </span>tutorial.py
</pre></div>
</div>
<p>What does this code do?
First we define a function <code class="code docutils literal notranslate"><span class="pre">MyApp</span></code> which is decorated by
<a class="reference internal" href="stubs/edifice.component.html#edifice.component" title="edifice.component"><code class="xref py py-func docutils literal notranslate"><span class="pre">@component</span></code></a>.
The <code class="code docutils literal notranslate"><span class="pre">MyApp</span></code> component is the top-level Element of our application.</p>
<p><a class="reference internal" href="stubs/edifice.HBoxView.html#edifice.HBoxView" title="edifice.HBoxView"><code class="xref py py-class docutils literal notranslate"><span class="pre">HBoxView</span></code></a> is an example of
a base <a class="reference internal" href="stubs/edifice.QtWidgetElement.html#edifice.QtWidgetElement" title="edifice.QtWidgetElement"><code class="xref py py-class docutils literal notranslate"><span class="pre">QtWidgetElement</span></code></a>.
The HBoxView can have children. To establish the HBoxView as a parent Element and
then declare its children, we use a
<a class="reference external" href="https://docs.python.org/3/reference/compound_stmts.html#with">with statement</a>
context. Elements inside the <code class="code docutils literal notranslate"><span class="pre">with</span></code> context are children.</p>
<p>In HTML or XML or React JSX, we might have written it as:</p>
<div class="highlight-xml notranslate"><div class="highlight"><pre><span></span><span class="nt"><Window></span>
<span class="w"> </span><span class="nt"><HBoxView></span>
<span class="w"> </span><span class="nt"><Label</span><span class="w"> </span><span class="na">text=</span><span class="s">"Measurement in meters"</span><span class="w"> </span><span class="nt">/></span>
<span class="w"> </span><span class="nt"><TextInput</span><span class="w"> </span><span class="na">text=</span><span class="s">""</span><span class="w"> </span><span class="nt">/></span>
<span class="w"> </span><span class="nt"><Label</span><span class="w"> </span><span class="na">text=</span><span class="s">"Measurement in feet"</span><span class="w"> </span><span class="nt">/></span>
<span class="w"> </span><span class="nt"></HBoxView></span>
<span class="nt"></Window></span>
</pre></div>
</div>
<p>We pass the component <code class="code docutils literal notranslate"><span class="pre">MyApp</span></code>
to an <a class="reference internal" href="stubs/edifice.App.html#edifice.App" title="edifice.App"><code class="xref py py-class docutils literal notranslate"><span class="pre">App</span></code></a>,
which is responsible for actually doing the rendering.
It takes the description of each Element, and it decides when and how to render it and its children.
It does so by monitoring the <strong>state</strong> of each Element, and it will re-render
when the Element <strong>state</strong> changes.</p>
<p>We can change the formatting of the <a class="reference internal" href="stubs/edifice.Label.html#edifice.Label" title="edifice.Label"><code class="xref py py-class docutils literal notranslate"><span class="pre">Label</span></code></a>, <a class="reference internal" href="stubs/edifice.TextInput.html#edifice.TextInput" title="edifice.TextInput"><code class="xref py py-class docutils literal notranslate"><span class="pre">TextInput</span></code></a>, and
<a class="reference internal" href="stubs/edifice.HBoxView.html#edifice.HBoxView" title="edifice.HBoxView"><code class="xref py py-class docutils literal notranslate"><span class="pre">HBoxView</span></code></a> using Qt <a class="reference internal" href="styling.html"><span class="doc">styling</span></a>,
which is similar to CSS styling.
Here, we want to add padding between the HBoxView and Window boundary,
make the Labels shorter, and add a margin between the Label and TextInput.</p>
<div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="kn">from</span> <span class="nn">edifice</span> <span class="kn">import</span> <span class="n">App</span><span class="p">,</span> <span class="n">Label</span><span class="p">,</span> <span class="n">TextInput</span><span class="p">,</span> <span class="n">HBoxView</span><span class="p">,</span> <span class="n">Window</span><span class="p">,</span> <span class="n">component</span>
<span class="nd">@component</span>
<span class="k">def</span> <span class="nf">MyApp</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="n">meters_label_style</span> <span class="o">=</span> <span class="p">{</span><span class="s2">"min-width"</span><span class="p">:</span> <span class="mi">170</span><span class="p">}</span>
<span class="n">feet_label_style</span> <span class="o">=</span> <span class="p">{</span><span class="s2">"margin-left"</span><span class="p">:</span> <span class="mi">20</span><span class="p">,</span> <span class="s2">"width"</span><span class="p">:</span> <span class="mi">220</span><span class="p">}</span>
<span class="n">input_style</span> <span class="o">=</span> <span class="p">{</span><span class="s2">"padding"</span><span class="p">:</span> <span class="mi">2</span><span class="p">,</span> <span class="s2">"width"</span><span class="p">:</span> <span class="mi">120</span><span class="p">}</span>
<span class="k">with</span> <span class="n">Window</span><span class="p">():</span>
<span class="k">with</span> <span class="n">HBoxView</span><span class="p">(</span><span class="n">style</span><span class="o">=</span><span class="p">{</span><span class="s2">"padding"</span><span class="p">:</span> <span class="mi">10</span><span class="p">}):</span>
<span class="n">Label</span><span class="p">(</span><span class="s2">"Measurement in meters:"</span><span class="p">,</span> <span class="n">style</span><span class="o">=</span><span class="n">meters_label_style</span><span class="p">)</span>
<span class="n">TextInput</span><span class="p">(</span><span class="s2">""</span><span class="p">,</span> <span class="n">style</span><span class="o">=</span><span class="n">input_style</span><span class="p">)</span>
<span class="n">Label</span><span class="p">(</span><span class="s2">"Measurement in feet:"</span><span class="p">,</span> <span class="n">style</span><span class="o">=</span><span class="n">feet_label_style</span><span class="p">)</span>
<span class="k">if</span> <span class="vm">__name__</span> <span class="o">==</span> <span class="s2">"__main__"</span><span class="p">:</span>
<span class="n">App</span><span class="p">(</span><span class="n">MyApp</span><span class="p">())</span><span class="o">.</span><span class="n">start</span><span class="p">()</span>
</pre></div>
</div>
<p>Our application still doesn’t do anything, however. Let’s add an <code class="code docutils literal notranslate"><span class="pre">on_change</span></code>
event handler <strong>prop</strong> for the <a class="reference internal" href="stubs/edifice.TextInput.html#edifice.TextInput" title="edifice.TextInput"><code class="xref py py-class docutils literal notranslate"><span class="pre">TextInput</span></code></a>.
the <code class="code docutils literal notranslate"><span class="pre">on_change</span></code> <strong>prop</strong> function will be called whenever the contents in the
text input changes due to user action.</p>
<div class="highlight-python notranslate"><div class="highlight"><pre><span></span><span class="kn">from</span> <span class="nn">edifice</span> <span class="kn">import</span> <span class="n">App</span><span class="p">,</span> <span class="n">Label</span><span class="p">,</span> <span class="n">TextInput</span><span class="p">,</span> <span class="n">HBoxView</span><span class="p">,</span> <span class="n">Window</span><span class="p">,</span> <span class="n">component</span><span class="p">,</span> <span class="n">use_state</span>
<span class="n">METERS_TO_FEET</span> <span class="o">=</span> <span class="mf">3.28084</span>
<span class="nd">@component</span>
<span class="k">def</span> <span class="nf">MyApp</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="n">meters</span><span class="p">,</span> <span class="n">meters_set</span> <span class="o">=</span> <span class="n">use_state</span><span class="p">(</span><span class="s2">"0.0"</span><span class="p">)</span>
<span class="n">meters_label_style</span> <span class="o">=</span> <span class="p">{</span><span class="s2">"width"</span><span class="p">:</span> <span class="mi">170</span><span class="p">}</span>
<span class="n">feet_label_style</span> <span class="o">=</span> <span class="p">{</span><span class="s2">"margin-left"</span><span class="p">:</span> <span class="mi">20</span><span class="p">,</span> <span class="s2">"width"</span><span class="p">:</span> <span class="mi">220</span><span class="p">}</span>
<span class="n">input_style</span> <span class="o">=</span> <span class="p">{</span><span class="s2">"padding"</span><span class="p">:</span> <span class="mi">2</span><span class="p">,</span> <span class="s2">"width"</span><span class="p">:</span> <span class="mi">120</span><span class="p">}</span>
<span class="k">with</span> <span class="n">Window</span><span class="p">():</span>
<span class="k">with</span> <span class="n">HBoxView</span><span class="p">(</span><span class="n">style</span><span class="o">=</span><span class="p">{</span><span class="s2">"padding"</span><span class="p">:</span> <span class="mi">10</span><span class="p">}):</span>
<span class="n">Label</span><span class="p">(</span><span class="s2">"Measurement in meters:"</span><span class="p">,</span> <span class="n">style</span><span class="o">=</span><span class="n">meters_label_style</span><span class="p">)</span>
<span class="n">TextInput</span><span class="p">(</span><span class="n">meters</span><span class="p">,</span> <span class="n">style</span><span class="o">=</span><span class="n">input_style</span><span class="p">,</span> <span class="n">on_change</span><span class="o">=</span><span class="n">meters_set</span><span class="p">)</span>
<span class="k">try</span><span class="p">:</span>
<span class="n">feet</span> <span class="o">=</span> <span class="sa">f</span><span class="s2">"</span><span class="si">{</span><span class="nb">float</span><span class="p">(</span><span class="n">meters</span><span class="p">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">METERS_TO_FEET</span><span class="w"> </span><span class="si">:</span><span class="s2">.3f</span><span class="si">}</span><span class="s2">"</span>
<span class="n">Label</span><span class="p">(</span><span class="sa">f</span><span class="s2">"Measurement in feet: </span><span class="si">{</span><span class="n">feet</span><span class="si">}</span><span class="s2">"</span><span class="p">,</span> <span class="n">style</span><span class="o">=</span><span class="n">feet_label_style</span><span class="p">)</span>
<span class="k">except</span> <span class="ne">ValueError</span><span class="p">:</span> <span class="c1"># Could not convert string to float</span>
<span class="k">pass</span> <span class="c1"># So don't render the Label</span>
<span class="k">if</span> <span class="vm">__name__</span> <span class="o">==</span> <span class="s2">"__main__"</span><span class="p">:</span>
<span class="n">App</span><span class="p">(</span><span class="n">MyApp</span><span class="p">())</span><span class="o">.</span><span class="n">start</span><span class="p">()</span>
</pre></div>
</div>
<p><code class="code docutils literal notranslate"><span class="pre">meters</span></code> is a <strong>state</strong> variable in our component <code class="code docutils literal notranslate"><span class="pre">MyApp</span></code>,
so we have to use the <a class="reference internal" href="stubs/edifice.use_state.html#edifice.use_state" title="edifice.use_state"><code class="xref py py-func docutils literal notranslate"><span class="pre">use_state()</span></code></a> hook.
<a class="reference internal" href="stubs/edifice.use_state.html#edifice.use_state" title="edifice.use_state"><code class="xref py py-func docutils literal notranslate"><span class="pre">use_state()</span></code></a> returns a tuple with the current value
of <code class="code docutils literal notranslate"><span class="pre">meters</span></code>, and also a <strong>state</strong> setter function which we can use to set
a new value for <code class="code docutils literal notranslate"><span class="pre">meters</span></code>.</p>
<ul class="simple">
<li><p><code class="code docutils literal notranslate"><span class="pre">meters</span></code> has type <code class="code docutils literal notranslate"><span class="pre">str</span></code>.</p></li>
<li><p><code class="code docutils literal notranslate"><span class="pre">meters_set</span></code> setter function has type <code class="code docutils literal notranslate"><span class="pre">Callable[[str],</span> <span class="pre">None]</span></code>.</p></li>
</ul>
<p>We assigned the <code class="code docutils literal notranslate"><span class="pre">meters_set</span></code> <strong>state</strong> setter function as
the <code class="code docutils literal notranslate"><span class="pre">on_change</span></code> <strong>prop</strong> for the <a class="reference internal" href="stubs/edifice.TextInput.html#edifice.TextInput" title="edifice.TextInput"><code class="xref py py-class docutils literal notranslate"><span class="pre">TextInput</span></code></a>.
Whenever the user types in the text input, the state will be set and
the UI will re-render.</p>
<p>Think of the <a class="reference internal" href="stubs/edifice.component.html#edifice.component" title="edifice.component"><code class="xref py py-func docutils literal notranslate"><span class="pre">@component</span></code></a> function as a map from the
<code class="code docutils literal notranslate"><span class="pre">meters</span></code> <strong>state</strong> to an Element tree.</p>
<p>In the <a class="reference internal" href="stubs/edifice.component.html#edifice.component" title="edifice.component"><code class="xref py py-func docutils literal notranslate"><span class="pre">@component</span></code></a> function, we read the value of <code class="code docutils literal notranslate"><span class="pre">meters</span></code>
and convert it to feet,
and we render the text input and label Elements.</p>
<p>Now we want to add conversion from feet to meters. Instead of copying our code and repeating
it for each measurement pair, we can factor out the conversion logic into its own component.
We pass the conversion parameters into the component as <strong>props</strong> arguments:</p>
<div class="highlight-default notranslate"><div class="highlight"><pre><span></span><span class="kn">from</span> <span class="nn">edifice</span> <span class="kn">import</span> <span class="n">App</span><span class="p">,</span> <span class="n">Label</span><span class="p">,</span> <span class="n">TextInput</span><span class="p">,</span> <span class="n">HBoxView</span><span class="p">,</span> <span class="n">Window</span><span class="p">,</span> <span class="n">component</span><span class="p">,</span> <span class="n">use_state</span>
<span class="n">METERS_TO_FEET</span> <span class="o">=</span> <span class="mf">3.28084</span>
<span class="nd">@component</span>
<span class="k">def</span> <span class="nf">ConversionWidget</span><span class="p">(</span><span class="bp">self</span><span class="p">,</span> <span class="n">from_unit</span><span class="p">:</span><span class="nb">str</span><span class="p">,</span> <span class="n">to_unit</span><span class="p">:</span><span class="nb">str</span><span class="p">,</span> <span class="n">factor</span><span class="p">:</span><span class="nb">float</span><span class="p">):</span>
<span class="n">current_text</span><span class="p">,</span> <span class="n">current_text_set</span> <span class="o">=</span> <span class="n">use_state</span><span class="p">(</span><span class="s2">"0.0"</span><span class="p">)</span>
<span class="n">from_label_style</span> <span class="o">=</span> <span class="p">{</span><span class="s2">"min-width"</span><span class="p">:</span> <span class="mi">170</span><span class="p">}</span>
<span class="n">to_label_style</span> <span class="o">=</span> <span class="p">{</span><span class="s2">"margin-left"</span><span class="p">:</span> <span class="mi">60</span><span class="p">,</span> <span class="s2">"min-width"</span><span class="p">:</span> <span class="mi">220</span><span class="p">}</span>
<span class="n">input_style</span> <span class="o">=</span> <span class="p">{</span><span class="s2">"padding"</span><span class="p">:</span> <span class="mi">2</span><span class="p">,</span> <span class="s2">"width"</span><span class="p">:</span> <span class="mi">120</span><span class="p">}</span>
<span class="k">with</span> <span class="n">HBoxView</span><span class="p">(</span><span class="n">style</span><span class="o">=</span><span class="p">{</span><span class="s2">"padding"</span><span class="p">:</span> <span class="mi">10</span><span class="p">}):</span>
<span class="n">Label</span><span class="p">(</span><span class="sa">f</span><span class="s2">"Measurement in </span><span class="si">{</span><span class="n">from_unit</span><span class="si">}</span><span class="s2">:"</span><span class="p">,</span> <span class="n">style</span><span class="o">=</span><span class="n">from_label_style</span><span class="p">)</span>
<span class="n">TextInput</span><span class="p">(</span><span class="n">current_text</span><span class="p">,</span> <span class="n">style</span><span class="o">=</span><span class="n">input_style</span><span class="p">,</span> <span class="n">on_change</span><span class="o">=</span><span class="n">current_text_set</span><span class="p">)</span>
<span class="k">try</span><span class="p">:</span>
<span class="n">to_text</span> <span class="o">=</span> <span class="sa">f</span><span class="s2">"</span><span class="si">{</span><span class="nb">float</span><span class="p">(</span><span class="n">current_text</span><span class="p">)</span><span class="w"> </span><span class="o">*</span><span class="w"> </span><span class="n">factor</span><span class="w"> </span><span class="si">:</span><span class="s2">.3f</span><span class="si">}</span><span class="s2">"</span>
<span class="n">Label</span><span class="p">(</span><span class="sa">f</span><span class="s2">"Measurement in </span><span class="si">{</span><span class="n">to_unit</span><span class="si">}</span><span class="s2">: </span><span class="si">{</span><span class="n">to_text</span><span class="si">}</span><span class="s2">"</span><span class="p">,</span> <span class="n">style</span><span class="o">=</span><span class="n">to_label_style</span><span class="p">)</span>
<span class="k">except</span> <span class="ne">ValueError</span><span class="p">:</span> <span class="c1"># Could not convert string to float</span>
<span class="k">pass</span> <span class="c1"># So don't render the Label</span>
<span class="nd">@component</span>
<span class="k">def</span> <span class="nf">MyApp</span><span class="p">(</span><span class="bp">self</span><span class="p">):</span>
<span class="k">with</span> <span class="n">Window</span><span class="p">(</span><span class="n">title</span><span class="o">=</span><span class="s2">"Measurement Conversion"</span><span class="p">):</span>
<span class="n">ConversionWidget</span><span class="p">(</span><span class="s2">"meters"</span><span class="p">,</span> <span class="s2">"feet"</span><span class="p">,</span> <span class="n">METERS_TO_FEET</span><span class="p">)</span>
<span class="n">ConversionWidget</span><span class="p">(</span><span class="s2">"feet"</span><span class="p">,</span> <span class="s2">"meters"</span><span class="p">,</span> <span class="mi">1</span> <span class="o">/</span> <span class="n">METERS_TO_FEET</span><span class="p">)</span>
<span class="k">if</span> <span class="vm">__name__</span> <span class="o">==</span> <span class="s2">"__main__"</span><span class="p">:</span>
<span class="n">App</span><span class="p">(</span><span class="n">MyApp</span><span class="p">())</span><span class="o">.</span><span class="n">start</span><span class="p">()</span>
</pre></div>
</div>
<p>We can use the <a class="reference internal" href="developer_tools.html"><span class="doc">Edifice Runner</span></a> to run our application.</p>
<p>First install <code class="code docutils literal notranslate"><span class="pre">watchdog</span></code>.</p>
<div class="highlight-shell notranslate"><div class="highlight"><pre><span></span>pip<span class="w"> </span>install<span class="w"> </span>watchdog
</pre></div>
</div>
<p>Then run the application with the <a class="reference internal" href="developer_tools.html"><span class="doc">Edifice Runner</span></a>.
This will run our application with <strong>Element Inspector</strong> and <strong>Hot-Reload</strong>.</p>
<div class="highlight-shell notranslate"><div class="highlight"><pre><span></span>python<span class="w"> </span>-m<span class="w"> </span>edifice<span class="w"> </span>--inspect<span class="w"> </span>tutorial.py<span class="w"> </span>MyApp
</pre></div>
</div>
<p>The Element Inspector allows us to see the current <strong>state</strong> and <strong>props</strong> for all Elements in a UI.
Type in the <a class="reference internal" href="stubs/edifice.TextInput.html#edifice.TextInput" title="edifice.TextInput"><code class="xref py py-class docutils literal notranslate"><span class="pre">TextInput</span></code></a> widget and see how the <strong>state</strong> changes.</p>
<p>Editing and saving the <code class="code docutils literal notranslate"><span class="pre">ConversionWidget</span></code> component source code will automatically
reload the component and update the UI. (Editing the <code class="code docutils literal notranslate"><span class="pre">MyApp</span></code> component will
not reload the UI, because Hot-Reload does not work for the root component.)</p>
</section>
</article>
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