Common up duplicate code

Glyn Normington · Glyn Normington · commit dbe4921c794c · 2013-09-16T14:32:08.000+01:00
[#56447064]
diff --git a/lib/java_buildpack/jre/memory/memory_size.rb b/lib/java_buildpack/jre/memory/memory_size.rb
@@ -79,8 +79,9 @@ def <=>(other)
     # @param [MemorySize] other the memory size to add
     # @return [MemorySize] the result
     def +(other)
-      raise "Cannot add an instance of #{other.class} to a MemorySize" unless other.is_a? MemorySize
-      MemorySize.from_numeric(@bytes + other.bytes)
+      memory_size_operation(other) do |self_bytes, other_bytes|
+        self_bytes + other_bytes
+      end
     end
 
     # Multiply this memory size by a numeric factor.
@@ -97,8 +98,9 @@ def *(other)
     # @param [MemorySize] other the memory size to subtract
     # @return [MemorySize] the result
     def -(other)
-      raise "Cannot subtract an instance of #{other.class} from a MemorySize" unless other.is_a? MemorySize
-      MemorySize.from_numeric(@bytes - other.bytes)
+      memory_size_operation(other) do |self_bytes, other_bytes|
+        self_bytes - other_bytes
+      end
     end
 
     # Divide a memory size by a memory size or a numeric value. The units are respected, so the result of diving by a
@@ -122,6 +124,11 @@ def /(other)
 
     KILO = 1024
 
+    def memory_size_operation(other)
+      raise "Invalid parameter: instance of #{other.class} is not a MemorySize" unless other.is_a? MemorySize
+      MemorySize.from_numeric(yield @bytes, other.bytes)
+    end
+
     def self.is_integer(v)
       f = Float(v)
       f && f.floor == f
diff --git a/spec/java_buildpack/jre/memory/memory_size_spec.rb b/spec/java_buildpack/jre/memory/memory_size_spec.rb
@@ -83,15 +83,15 @@ module JavaBuildpack::Jre
     end
 
     it 'should fail when a numeric is subtracted from a memory size' do
-      expect { ONE_MEG - 1 }.to raise_error(/Cannot\ subtract/)
+      expect { ONE_MEG - 1 }.to raise_error(/Invalid parameter: instance of Fixnum is not a MemorySize/)
     end
 
     it 'should add memory values correctly' do
       expect(HALF_A_MEG + HALF_A_MEG).to eq(ONE_MEG)
     end
 
     it 'should fail when a numeric is added to a memory size' do
-      expect { ONE_MEG + 1 }.to raise_error(/Cannot\ add/)
+      expect { ONE_MEG + 1 }.to raise_error(/Invalid parameter: instance of Fixnum is not a MemorySize/)
     end
 
     it 'should divide a memory size by a numeric correctly' do
