Merge pull request #182 from stencilproject/blocks-cache

Caching rendered blocks content to reuse them in further calls

CHANGELOG.md

@@ -26,6 +26,10 @@
 - Added support for adding default whitespace trimming behaviour to an environment.  
   [Yonas Kolb](https://github.com/yonaskolb)
   [#287](https://github.com/stencilproject/Stencil/pull/287)
+- Blocks now can be used repeatedly in the template. When block is rendered for the first time its content will be cached and it can be rendered again later using `{{ block.block_name }}`.  
+  [Ilya Puchka](https://github.com/ilyapuchka)
+  [#158](https://github.com/stencilproject/Stencil/issues/158)
+  [#182](https://github.com/stencilproject/Stencil/pull/182)
 
 ### Deprecations
 

Sources/Stencil/Context.swift

@@ -85,4 +85,19 @@ public class Context {
 
     return accumulator
   }
+
+  /// Cache result of block by its name in the context top-level, so that it can be later rendered
+  /// via `{{ block.name }}`
+  ///
+  /// - Parameters:
+  ///   - name: The name of the stored block
+  ///   - content: The block's rendered content
+  public func cacheBlock(_ name: String, content: String) {
+    if var block = dictionaries.first?["block"] as? [String: String] {
+      block[name] = content
+      dictionaries[0]["block"] = block
+    } else {
+      dictionaries.insert(["block": [name: content]], at: 0)
+    }
+  }
 }

Sources/Stencil/Inheritance.swift

@@ -151,6 +151,8 @@ class BlockNode: NodeType {
       }
     }
 
-    return try renderNodes(nodes, context)
+    let result = try renderNodes(nodes, context)
+    context.cacheBlock(name, content: result)
+    return result
   }
 }

Tests/StencilTests/InheritanceSpec.swift

@@ -52,4 +52,22 @@ final class InheritanceTests: XCTestCase {
       """
     }
   }
+
+  func testInheritanceCache() {
+    it("can call block twice") {
+      let template: Template = "{% block repeat %}Block{% endblock %}{{ block.repeat }}"
+      try expect(try template.render()) == "BlockBlock"
+    }
+
+    it("renders child content when calling block twice in base template") {
+      let template = try self.environment.loadTemplate(name: "child-repeat.html")
+      try expect(try template.render()) == """
+      Super_Header Child_Header
+      Child_Body
+      Repeat
+      Super_Header Child_Header
+      Child_Body
+      """
+    }
+  }
 }

Tests/StencilTests/fixtures/base-repeat.html

@@ -0,0 +1,5 @@
+{% block header %}Header{% endblock %}
+{% block body %}Body{% endblock %}
+Repeat
+{{ block.header }}
+{{ block.body }}

Tests/StencilTests/fixtures/child-repeat.html

@@ -0,0 +1,3 @@
+{% extends "base-repeat.html" %}
+{% block header %}Super_{{ block.super }} Child_Header{% endblock %}
+{% block body %}Child_Body{% endblock %}

docs/templates.rst

@@ -141,7 +141,7 @@ Let's take a look at an example. Here is our base template (``base.html``):
     </html>
 
 This example declares three blocks, ``title``, ``sidebar`` and ``content``. We
-can use the ``{% extends %}`` template tag to inherit from out base template
+can use the ``{% extends %}`` template tag to inherit from our base template
 and then use ``{% block %}`` to override any blocks from our base template.
 
 A child template might look like the following:
@@ -195,3 +195,5 @@ inheritance is the following three-level approach:
   extend ``base.html`` and include section-specific styles/design.
 * Create individual templates for each type of page, such as a news article or
   blog entry. These templates extend the appropriate section template.
+
+You can render block's content more than once by using ``{{ block.name }}`` **after** a block is defined.