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lib/phoenix_component.ex

defmodule Phoenix.Component do
@moduledoc """
API for function components.
A function component is any function that receives
an assigns map as argument and returns a rendered
struct built with [the `~H` sigil](`Phoenix.LiveView.Helpers.sigil_H/2`)..
Here is an example:
defmodule MyComponent do
use Phoenix.Component
# Optionally also bring the HTML helpers
# use Phoenix.HTML
def greet(assigns) do
~H"\""
<p>Hello, <%= assigns.name %></p>
"\""
end
end
The component can be invoked as a regular function:
MyComponent.greet(%{name: "Jane"})
But it is typically invoked using the function component
syntax from the `~H` sigil:
~H"\""
<MyComponent.greet name="Jane" />
"\""
If the `MyComponent` module is imported or if the function
is defined locally, you can skip the module name:
~H"\""
<.greet name="Jane" />
"\""
Learn more about the `~H` sigil [in its documentation](`Phoenix.LiveView.Helpers.sigil_H/2`).
## `use Phoenix.Component`
Modules that have to define function components should call `use Phoenix.Component`
at the top. Doing so will import the functions from both `Phoenix.LiveView`
and `Phoenix.LiveView.Helpers` modules.
Note it is not necessary to `use Phoenix.Component` inside `Phoenix.LiveView`
and `Phoenix.LiveComponent`.
## Assigns
While inside a function component, it is recommended to use
the functions in `Phoenix.LiveView` to manipulate assigns.
For example, let's imagine a component that receives the first
name and last name and must compute the name assign. One option
would be:
def show_name(assigns) do
assigns = assign(assigns, :name, assigns.first_name <> assigns.last_name)
~H"\""
<p>Your name is: <%= @name %></p>
"\""
end
However, when possible, it may be cleaner to break the logic over function
calls instead of precomputed assigns:
def show_name(assigns) do
~H"\""
<p>Your name is: <%= full_name(@first_name, @last_name) %></p>
"\""
end
defp full_name(first_name, last_name), do: first_name <> last_name
## Blocks
It is also possible to give HTML blocks to function components
as in regular HTML tags. For example, you could create a
button component that looks like this:
def button(assigns) do
~H"\""
<button class="btn">
<%= render_block(@inner_block) %>
</button>
"\""
end
and now you can invoke it as:
<.button>
This renders <strong>inside</strong> the button!
</.button>
In a nutshell, the block given to the component is
assigned to `@inner_block` and then we use
[`render_block`](`Phoenix.LiveView.Helpers.render_block/2`)
to render it.
You can even have the component give a value back to
the caller, by using `let`. Imagine this component:
def unordered_list(assigns) do
~H"\""
<ul>
<%= for entry <- @entries do %>
<li><%= render_block(@inner_block, entry) %></li>
<% end %>
</ul>
"\""
end
And now you can invoke it as:
<.unordered_list let={entry} entries={~w(apple banana cherry)}>
I like <%= entry %>
</.unordered_list>
"""
@doc false
defmacro __using__(_) do
quote do
import Phoenix.LiveView
import Phoenix.LiveView.Helpers
end
end
end