Merge pull request #3023 from crystal-lang/feature/lazy_getter

Added lazy form to `Object#getter` macro. Fixes #3022
crystal-lang · Jul 21, 2016 · 765072c · 765072c
2 parents fecbc1c + 3e40bff
commit 765072c
Showing 2 changed files with 148 additions and 30 deletions.
diff --git a/spec/std/object_spec.cr b/spec/std/object_spec.cr
@@ -27,6 +27,14 @@ module ObjectSpec
     getter? getter9 : Bool = true
     getter? getter10 = true
 
+    getter(getter11) { 11 }
+
+    @@getter12_value = 12
+    getter getter12 : Int32 { @@getter12_value }
+
+    def self.getter12_value=(@@getter12_value)
+    end
+
     setter setter1
     setter setter2 : Int32
     setter setter3 : Int32 = 3
@@ -47,6 +55,9 @@ module ObjectSpec
     property? property9 : Bool = true
     property? property10 = true
 
+    property(property11) { 11 }
+    property property12 : Int32 { 10 + 2 }
+
     def initialize
       @getter1 = 1
       @getter2 = 2
@@ -137,6 +148,17 @@ describe Object do
       typeof(obj.@getter4).should eq(Int32)
       typeof(obj.getter4).should eq(Int32)
     end
+
+    it "defines lazy getter with block" do
+      obj = ObjectSpec::TestObject.new
+      obj.getter11.should eq(11)
+      obj.getter12.should eq(12)
+      ObjectSpec::TestObject.getter12_value = 24
+      obj.getter12.should eq(12)
+
+      obj2 = ObjectSpec::TestObject.new
+      obj2.getter12.should eq(24)
+    end
   end
 
   describe "getter!" do
@@ -251,6 +273,17 @@ describe Object do
       obj.property4 = 5
       obj.property4.should eq(5)
     end
+
+    it "defines lazy property with block" do
+      obj = ObjectSpec::TestObject.new
+      obj.property11.should eq(11)
+      obj.property11 = 12
+      obj.property11.should eq(12)
+
+      obj.property12.should eq(12)
+      obj.property12 = 13
+      obj.property12.should eq(13)
+    end
   end
 
   describe "property!" do

diff --git a/src/object.cr b/src/object.cr
@@ -251,25 +251,65 @@ class Object
   #   end
   # end
   # ```
-  macro getter(*names)
-    {% for name in names %}
-      {% if name.is_a?(TypeDeclaration) %}
-        @{{name}}
+  #
+  # If a block is given to the macro, a getter is generated
+  # with an instance variable that is lazily initialized with
+  # the block's contents:
+  #
+  # ```
+  # class Person
+  #   getter(birth_date) { Time.now }
+  # end
+  # ```
+  #
+  # Is the same as writing:
+  #
+  # ```
+  # class Person
+  #   def birth_date
+  #     @birth_date ||= Time.now
+  #   end
+  # end
+  # ```
+  macro getter(*names, &block)
+    {% if block %}
+      {% if names.size != 1 %}
+        {{ raise "only one argument can be passed to `getter` with a block" }}
+      {% end %}
 
-        def {{name.var.id}} : {{name.type}}
-          @{{name.var.id}}
-        end
-      {% elsif name.is_a?(Assign) %}
-        @{{name}}
+      {% name = names[0] %}
 
-        def {{name.target.id}}
-          @{{name.target.id}}
+      {% if name.is_a?(TypeDeclaration) %}
+        @{{name.var.id}} : {{name.type}}?
+
+        def {{name.var.id}}
+          @{{name.var.id}} ||= {{yield}}
         end
       {% else %}
         def {{name.id}}
-          @{{name.id}}
+          @{{name.id}} ||= {{yield}}
         end
       {% end %}
+    {% else %}
+      {% for name in names %}
+        {% if name.is_a?(TypeDeclaration) %}
+          @{{name}}
+
+          def {{name.var.id}} : {{name.type}}
+            @{{name.var.id}}
+          end
+        {% elsif name.is_a?(Assign) %}
+          @{{name}}
+
+          def {{name.target.id}}
+            @{{name.target.id}}
+          end
+        {% else %}
+          def {{name.id}}
+            @{{name.id}}
+          end
+        {% end %}
+      {% end %}
     {% end %}
   end
 
@@ -664,33 +704,78 @@ class Object
   #   end
   # end
   # ```
-  macro property(*names)
-    {% for name in names %}
-      {% if name.is_a?(TypeDeclaration) %}
-        @{{name}}
+  #
+  # If a block is given to the macro, a property is generated
+  # with an instance variable that is lazily initialized with
+  # the block's contents:
+  #
+  # ```
+  # class Person
+  #   property(birth_date) { Time.now }
+  # end
+  # ```
+  #
+  # Is the same as writing:
+  #
+  # ```
+  # class Person
+  #   def birth_date
+  #     @birth_date ||= Time.now
+  #   end
+  #
+  #   def birth_date=(@birth_date)
+  #   end
+  # end
+  # ```
+  macro property(*names, &block)
+    {% if block %}
+      {% if names.size != 1 %}
+        {{ raise "only one argument can be passed to `property` with a block" }}
+      {% end %}
 
-        def {{name.var.id}} : {{name.type}}
-          @{{name.var.id}}
-        end
+      {% name = names[0] %}
 
-        def {{name.var.id}}=(@{{name.var.id}} : {{name.type}})
-        end
-      {% elsif name.is_a?(Assign) %}
-        @{{name}}
+      setter {{name}}
 
-        def {{name.target.id}}
-          @{{name.target.id}}
-        end
+      {% if name.is_a?(TypeDeclaration) %}
+        @{{name.var.id}} : {{name.type}}?
 
-        def {{name.target.id}}=(@{{name.target.id}})
+        def {{name.var.id}}
+          @{{name.var.id}} ||= {{yield}}
         end
       {% else %}
         def {{name.id}}
-          @{{name.id}}
+          @{{name.id}} ||= {{yield}}
         end
+      {% end %}
+    {% else %}
+      {% for name in names %}
+        {% if name.is_a?(TypeDeclaration) %}
+          @{{name}}
 
-        def {{name.id}}=(@{{name.id}})
-        end
+          def {{name.var.id}} : {{name.type}}
+            @{{name.var.id}}
+          end
+
+          def {{name.var.id}}=(@{{name.var.id}} : {{name.type}})
+          end
+        {% elsif name.is_a?(Assign) %}
+          @{{name}}
+
+          def {{name.target.id}}
+            @{{name.target.id}}
+          end
+
+          def {{name.target.id}}=(@{{name.target.id}})
+          end
+        {% else %}
+          def {{name.id}}
+            @{{name.id}}
+          end
+
+          def {{name.id}}=(@{{name.id}})
+          end
+        {% end %}
       {% end %}
     {% end %}
   end