Ruby pro tips from Rails core committer Aaron Patterson
WHERE IS THAT METHOD?
Q: This code is calling a method, but I don't know where the method is defined. How can I find it?
A: Use the
methodmethod will return a method object and let you call
source_locationto find the method location. For example:
objecthas the instance method
unknown_method, this code will print the location of that method.
WHO IS CALLING ME?
Q: I'm inside a method, but I don't know who called this method. How can I find out?
A: Use the
callermethod will give you the current stack trace, so you can do
p callerand see who is calling you. Alternatively, just raise an exception, and you'll see the backtrace.
WHAT IS MY CLASS?
Q: I'm editing a method, but I'm not sure what class it's defined on. How can I find out?
A: Use the
classmethod. For example:
def foo p self.class end
This will print out the class of
selfwhich is your current instance.
WHAT IS MY SUPERCLASS?
Q: I am editing a method that calls
super, like this:
def foo # ... super # ... endI want to know where the superclass method is defined. How do I find it?
A: You can use the
superclassmethod on the class to get the superclass. For example:
def foo # ... p self.class.superclass.instance_method(:foo).source_location super # ... end
One caveat is that the method may not be defined on your superclass, but somewhere further up the inheritance chain. You can find that by using
ancestors. For example:
def foo # ... self.class.ancestors.each do |klass| next unless klass.method_defined?(:foo) p klass.instance_method(:foo).source_location end super # ... end
I NEED A DEBUGGER!
I personally don't use a debugger, but I've heard the
debuggergem is good.
Source: edx online BerkleyX course (saas engineering cs169x.1)
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