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def test
"Hello World"
end
p method(:test).call #"Hello World"
p method("test").call #"Hello World"
My question is: what happens when we pass a symbol to the call method? Will ruby convert the symbol to a String and then execute it? If so, then what is it's purpose?
And if not, then what actually happens? Can you please elaborate? Sorry if I fail to make myself clear.
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Ruby methods ALWAYS return the evaluated result of the last line of the expression unless an explicit return comes before it. If you wanted to explicitly return a value you can use the return keyword.
When you call a method on an object, Ruby looks for the implementation of that method. It looks in the following places and uses the first implementation it finds: Methods from the object's singleton class (an unnamed class that only exists for that object)
When Ruby executes the def keyword, it simply redefines it (whether the method already exists or not). This is called overriding. See the following example : def language puts("We are learning PHP") end def language puts("We are learning Ruby") end # Now call the method language.
When you execute def test ... outside of any explicit class or module definition, you are essentially in the Object class context, so test is now an instance method of Object
In irb ...
1.8.7 :001 > def test
1.8.7 :002?> "Hello world"
1.8.7 :003?> end
=> nil
1.8.7 :004 > Object.instance_methods.sort
=> ["==", "===", "=~", "__id__", "__send__", "class", "clone", "display", "dup", "enum_for", "eql?", "equal?", "extend", "freeze", "frozen?", "hash", "id", "inspect", "instance_eval", "instance_exec", "instance_of?", "instance_variable_defined?", "instance_variable_get", "instance_variable_set", "instance_variables", "is_a?", "kind_of?", "method", "methods", "nil?", "object_id", "private_methods", "protected_methods", "public_methods", "respond_to?", "send", "singleton_methods", "taint", "tainted?", "tap", "test", "to_a", "to_enum", "to_s", "type", "untaint"]
method is an instance method of the Object class which is inherited by essentially everything. When you call method outside of any explicit class or module definition, you are essentially invoking it as a method of the Object class, and that class is itself an instance of Class, which is a subclass of Object (sorry -- I know that's a bit confusing to follow).
So -- the method method takes a string or a symbol and returns an object encapsulating the bound method of that name on the same object that .method was called on. In this case, that's the test method bound to the Object object.
method(:test).call means call the test method of Object which is what you defined previously via def test ....
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