Add lambda slots

README.md

@@ -228,10 +228,55 @@ class BlogComponent < Phlex::HTML
 end
 ```
 
+#### Lambda slots
+Lambda slots are valuable when you prefer not to create another component for straightforward structures or when you need to render another view with specific parameters
+```ruby
+
+class BlogComponent < Phlex::HTML
+  include Phlex::Slotable
+
+  slot :header, ->(size:, &content) { render HeaderComponent.new(size: size, color: "blue"), &content }
+  slot :post, ->(featured:, &content) { span(class: featured ? "featured" : nil, &content) }, many: true
+end
+
+class MyPage < Phlex::HTML
+  def template
+    render BlogComponent.new do |blog|
+      blog.with_header(size: :lg) { "Hello World!" }
+
+      blog.with_post(featured: true) { "Post A" }
+      blog.with_post { "Post B" }
+      blog.with_post { "Post C" }
+    end
+  end
+end
+```
+
+You can access the internal view state within lambda slots.For example:
+```ruby
+class BlogComponent < Phlex::HTML
+  include Phlex::Slotable
+
+  slot :header, ->(size:, &content) { render HeaderComponent.new(size: size, color: @header_color), &content }
+
+  def initialize(header_color:)
+    @header_color = header_color
+  end
+end
+
+class MyPage < Phlex::HTML
+  def template
+    render BlogComponent.new(header_color: "red") do |blog|
+      blog.with_header(size: :lg) { "Hello World!" }
+    end
+  end
+end
+```
+
 ## Roadmap
-- Accepts Strings as view class name
-- Allow lambda slots
-- Allow polymorphic slots
+- ✅ ~~Accept Strings as view class name~~
+- ✅ ~~Allow lambda slots~~
+- 🕐 Allow polymorphic slots
 
 ## Development
 

lib/phlex/slotable.rb

@@ -12,6 +12,11 @@ module ClassMethods
       def slot(slot_name, callable = nil, many: false)
         include Phlex::DeferredRender
 
+        if callable.is_a?(Proc)
+          define_method :"__call_#{slot_name}__", &callable
+          private :"__call_#{slot_name}__"
+        end
+
         if many
           define_method :"with_#{slot_name}" do |*args, **kwargs, &block|
             instance_variable_set(:"@#{slot_name}_slots", []) unless instance_variable_defined?(:"@#{slot_name}_slots")
@@ -21,6 +26,8 @@ def slot(slot_name, callable = nil, many: false)
               block
             when String
               self.class.const_get(callable).new(*args, **kwargs, &block)
+            when Proc
+              -> { self.class.instance_method(:"__call_#{slot_name}__").bind_call(self, *args, **kwargs, &block) }
             else
               callable.new(*args, **kwargs, &block)
             end
@@ -44,6 +51,8 @@ def slot(slot_name, callable = nil, many: false)
               block
             when String
               self.class.const_get(callable).new(*args, **kwargs, &block)
+            when Proc
+              -> { self.class.instance_method(:"__call_#{slot_name}__").bind_call(self, *args, **kwargs, &block) }
             else
               callable.new(*args, **kwargs, &block)
             end

test/phlex/test_multi_slot_with_lambda.rb

@@ -0,0 +1,98 @@
+# frozen_string_literal: true
+
+require "test_helper"
+
+class Phlex::TestMultiSlotWithLambda < Minitest::Test
+  class HeadlineComponent < Phlex::HTML
+    include Phlex::Slotable
+
+    slot :icon
+    slot :title
+
+    def initialize(size:, bg_color:)
+      @size = size
+      @bg_color = bg_color
+    end
+
+    def template
+      div class: "headline text-#{@size} bg-#{@bg_color}" do
+        render icon_slot
+        render title_slot
+      end
+    end
+  end
+
+  class Blog < Phlex::HTML
+    include Phlex::Slotable
+
+    slot :post, ->(featured: false, &content) { p(class: featured ? "featured" : nil, &content) }, many: true
+    slot :headline, ->(size:, &content) do
+      render HeadlineComponent.new(size: size, bg_color: @headline_bg_color), &content
+    end, many: true
+
+    def initialize(headline_bg_color: nil)
+      @headline_bg_color = headline_bg_color
+    end
+
+    def template
+      if post_slots?
+        main do
+          headline_slots.each do |slot|
+            render slot
+          end
+          post_slots.each do |slot|
+            render slot
+          end
+        end
+      end
+
+      footer { post_slots.size }
+    end
+  end
+
+  def test_slots
+    output = Blog.new(headline_bg_color: "blue").call do |c|
+      c.with_post(featured: true) { "Post A" }
+      c.with_post { "Post B" }
+      c.with_post { "Post C" }
+
+      c.with_headline(size: "lg") do |h|
+        h.with_title { "Headline A" }
+        h.with_icon { h.i(class: "star") }
+      end
+      c.with_headline(size: "md") do |h|
+        h.with_title { "Headline B" }
+        h.with_icon { h.i(class: "heart") }
+      end
+    end
+
+    expected_html = <<~HTML.join_lines
+      <main>
+        <div class="headline text-lg bg-blue">
+          <i class="star"></i>
+          Headline A
+        </div>
+        <div class="headline text-md bg-blue">
+          <i class="heart"></i>
+          Headline B
+        </div>
+
+        <p class="featured">Post A</p>
+        <p>Post B</p>
+        <p>Post C</p>
+      </main>
+
+      <footer>
+        3
+      </footer>
+    HTML
+
+    assert_equal expected_html, output
+  end
+
+  def test_empty_slots
+    output = Blog.new.call
+
+    assert_equal output, "<footer>0</footer>"
+  end
+end

test/phlex/test_single_slot_with_lambda.rb

@@ -0,0 +1,78 @@
+# frozen_string_literal: true
+
+require "test_helper"
+
+class Phlex::TestSingleSlotWithLambda < Minitest::Test
+  class SubtitleComponent < Phlex::HTML
+    include Phlex::Slotable
+
+    slot :icon
+    slot :content
+
+    def initialize(size:, bg_color:)
+      @size = size
+      @bg_color = bg_color
+    end
+
+    def template(&content)
+      h3(class: "text-#{@size} bg-#{@bg_color}") do
+        render icon_slot
+        render content_slot
+      end
+    end
+  end
+
+  class Blog < Phlex::HTML
+    include Phlex::Slotable
+
+    slot :title, ->(size:, &content) { h1(class: "text-#{size}", &content) }
+    slot :subtitle, ->(size:, &content) do
+      render SubtitleComponent.new(size: size, bg_color: @subtitle_bg_color), &content
+    end
+
+    def initialize(subtitle_bg_color: nil)
+      @subtitle_bg_color = subtitle_bg_color
+    end
+
+    def template
+      div id: "header" do
+        render title_slot if title_slot?
+        render subtitle_slot if subtitle_slot?
+      end
+
+      main { "My posts" }
+    end
+  end
+
+  def test_slot
+    output = Blog.new(subtitle_bg_color: "gray").call do |c|
+      c.with_title(size: :lg) { "Hello World!" }
+      c.with_subtitle(size: :sm) do |s|
+        s.with_icon { s.i(class: "home") }
+        s.with_content { "Welcome to your posts" }
+      end
+    end
+
+    assert_equal output, <<~HTML.join_lines
+      <div id="header">
+        <h1 class="text-lg">Hello World!</h1>
+        <h3 class="text-sm bg-gray">
+          <i class="home"></i>
+          Welcome to your posts
+        </h3>
+      </div>
+      <main>
+        My posts
+      </main>
+    HTML
+  end
+
+  def test_empty_slot
+    output = Blog.new.call
+
+    assert_equal output, <<~HTML.join_lines
+      <div id="header"></div>
+      <main>My posts</main>
+    HTML
+  end
+end