From 8806a202ee9863811d3cc5d46511f5786624bafd Mon Sep 17 00:00:00 2001
From: Oleg Andreev <oleganza@idbns.com>
Date: Fri, 2 May 2008 01:02:44 +0400
Subject: [PATCH] added helper Kernel#extract to work with method overloading
 (useful for complicated APIs like View#find)

---
 lib/strokedb/core_ext/kernel.rb            | 28 +++++++++++++++
 spec/lib/strokedb/core_ext/extract_spec.rb | 42 ++++++++++++++++++++++
 2 files changed, 70 insertions(+)
 create mode 100644 spec/lib/strokedb/core_ext/extract_spec.rb

diff --git a/lib/strokedb/core_ext/kernel.rb b/lib/strokedb/core_ext/kernel.rb
index 96ea8116..18589d74 100644
--- a/lib/strokedb/core_ext/kernel.rb
+++ b/lib/strokedb/core_ext/kernel.rb
@@ -15,4 +15,32 @@ def require_one_of(*args)
     end
     
   end
+  
+  # Helps to extract arguments for an overloaded methods:
+  #   def some_method(*args)
+  #     store, name, options = extract(Store, String, Hash, args)
+  #   end
+  #
+  # This method tries to extract arguments according to their type.
+  # If the correct type is missing, var is set to nil.
+  # If some of the input arguments are not matched, ArgumentError is raised.
+  #
+  def extract(*template_and_args)
+    args = template_and_args.pop
+    result = []
+        
+    args.each do |a|
+      unless while t = template_and_args.shift
+          if t === a
+            result << a
+            break(true) 
+          else
+            result << nil
+          end
+        end
+        raise ArgumentError, "Unexpected argument #{a.inspect} is passed!"
+      end
+    end
+    result + template_and_args.map{ nil }
+  end
 end
\ No newline at end of file
diff --git a/spec/lib/strokedb/core_ext/extract_spec.rb b/spec/lib/strokedb/core_ext/extract_spec.rb
new file mode 100644
index 00000000..cab3f573
--- /dev/null
+++ b/spec/lib/strokedb/core_ext/extract_spec.rb
@@ -0,0 +1,42 @@
+require File.dirname(__FILE__) + '/spec_helper'
+
+describe "Kernel#extract" do
+  
+  it "should correctly extract various arguments" do
+    extract(Regexp, String, Hash, [          ]).should == [nil, nil, nil]
+    
+    extract(Regexp, String, Hash, [/a/       ]).should == [/a/, nil, nil]
+    extract(Regexp, String, Hash, [    "a"   ]).should == [nil, "a", nil]
+    extract(Regexp, String, Hash, [    {1=>2}]).should == [nil, nil, {1=>2}]
+    
+    extract(Regexp, String, Hash, [//, ""    ]).should == [//,  "",  nil]
+    extract(Regexp, String, Hash, [//,     {}]).should == [//,  nil, {} ]
+    extract(Regexp, String, Hash, [    "", {}]).should == [nil,  "",  {}]
+    
+    extract(Regexp, String, Hash, [//, "", {}]).should == [//,  "",  {} ]
+  end
+  
+  it "should raise ArgumentError when wrong arguments are passed" do
+    
+    bad_case(Regexp, String, Hash, [123])
+    bad_case(Regexp, String, Hash, ["", //])
+    bad_case(Regexp, String, Hash, [{}, ""])
+    bad_case(Regexp, String, Hash, [true])
+    bad_case(Regexp, String, Hash, [false])
+    bad_case(Regexp, String, Hash, [//,false])
+    bad_case(Regexp, String, Hash, [nil])
+    bad_case(Regexp, String, Hash, ["", nil])
+    bad_case(Regexp, String, Hash, [nil, nil])
+    bad_case(Regexp, String, Hash, [{}, {}])
+    bad_case(Regexp, String, Hash, [//, //])
+    bad_case(Regexp, String, Hash, [ [] ])
+    bad_case(Regexp, String, Hash, [Object.new])
+    bad_case(Regexp, String, Hash, [Object.new, Object.new])
+    
+  end
+  
+  def bad_case(*args)
+    lambda { extract(*args) }.should raise_error(ArgumentError)
+  end
+  
+end
\ No newline at end of file