invoke methods

README.md

@@ -70,6 +70,19 @@ repo = owner: "pypy", slug: "pypy", followers: [...]
 # "pypy/pypy has 516 followers"
 ```
 
+If the referenced property is a method, it is invoked and the result is used
+as the replacement string:
+
+```coffeescript
+me = name: "David", dob: new Date "26 Apr 1984"
+
+"{name} was born in {dob.getFullYear}".format(me)
+# "David was born in 1984"
+
+"{pop}{pop}{pop}".format(["one", "two", "three"])
+# "threetwoone"
+```
+
 ### String.prototype.format.transformers
 
 “Transformers” can be attached to `String.prototype.format.transformers`:

spec/stringformat_spec.coffee

@@ -47,6 +47,12 @@ describe 'String::format', ->
     bobby = first_name: 'Bobby', last_name: 'Fischer'
     '{first_name} {last_name}'.format(bobby).should_be 'Bobby Fischer'
 
+  it 'invokes methods', ->
+    '{0.toLowerCase}'.format('III').should_be 'iii'
+    '{0.toUpperCase}'.format('iii').should_be 'III'
+    '{0.getFullYear}'.format(new Date '26 Apr 1984').should_be '1984'
+    '{pop}{pop}{pop}'.format(['one', 'two', 'three']).should_be 'threetwoone'
+
   String::format.transformers.s = -> 's' unless +this is 1
 
   it 'applies transformers to explicit positional arguments', ->

string-format.coffee

@@ -31,7 +31,8 @@ lookup = (object, key) ->
   while match = /(.+?)[.](.+)/.exec key
     object = object[match[1]]
     key = match[2]
-  object[key]
+  value = object[key]
+  if typeof value is 'function' then value.call object else value
 
 format.transformers = {}