The methods in a module may be instance methods or module methods. Instance methods appear as methods in a class when the module is included, module methods do not.
Conversely, module methods may be called without creating an encapsulating object, while instance methods may not. In the descriptions that follow, the parameter sym refers to a symbol, which is either a quoted string or a Symbol such as :name. In the first form, returns an array of the names of all constants accessible from the point of call.
This list includes the names of all modules and classes defined in the global scope. Creates a new anonymous module. Assign the module to a constant name starting uppercase if you want to treat it like a regular module. Returns an array of all modules used in the current scope. The ordering of modules in the resulting array is not defined. Returns true if mod is a subclass of other.
Returns nil if there's no relationship between the two. Returns true if mod is a subclass of other or is the same as other. Typically, this method is overridden in descendant classes to provide class-specific meaning. The eql? This is used by Hash to test members for equality. For objects of class Object , eql?
Subclasses normally continue this tradition by aliasing eql? Case Equality—Returns true if obj is an instance of mod or an instance of one of mod 's descendants. Of limited use for modules, but can be used in case statements to classify objects by class. Returns true if mod is an ancestor of other.
Returns true if mod is an ancestor of other , or the two modules are the same. This can be used to retain access to methods that are overridden. Defines a named attribute for this module, where the name is symbol. String arguments are converted to symbols. Creates instance variables and corresponding methods that return the value of each instance variable. Creates an accessor method to allow assignment to the attribute symbol. Registers filename to be loaded using Kernel::require the first time that module which may be a String or a symbol is accessed in the namespace of mod.
Returns filename to be loaded if name is registered as autoload in the namespace of mod. This can be used to add methods to a class. The optional filename and lineno parameters set the text for error messages.
The method defined in the block will belong to the receiver. Any arguments passed to the method will be passed to the block.
This can be used if the block needs to access instance variables. Returns true if the given class variable is defined in obj. Returns the value of the given class variable or throws a NameError exception. The part of the variable name should be included for regular class variables.
Sets the class variable named by symbol to the given object. If the class variable name is passed as a string, that string is converted to a symbol. Returns an array of the names of class variables in mod. This includes the names of class variables in any included modules, unless the inherit parameter is set to false. If mod is a Module , additionally Object and its ancestors are checked:.
In each of the checked classes or modules, if the constant is not present but there is an autoload for it, true is returned directly without autoloading:.
Checks for a constant with the given name in mod. If inherit is set, the lookup will also search the ancestors and Object if mod is a Module. The value of the constant is returned if a definition is found, otherwise a NameError is raised. This method will recursively look up constant names if a namespaced class name is provided.
Improve this question. Mike Mike 1 1 gold badge 3 3 silver badges 4 4 bronze badges. Add a comment. Active Oldest Votes. You can't include one module in another exactly, but you can tell a module to include other modules in the class into which it's included: module Bmodule def greet puts 'hello world' end end module Amodule def self.
Improve this answer. John Bachir Pan Thomakos Pan Thomakos 33k 9 9 gold badges 84 84 silver badges 84 84 bronze badges. This I was able to get to work, although it makes for a huge block wthin klass. You don't have to do anything special to get this to work, but you should make sure that you aren't setting the value of MYCONST more than once - that is what causes the warning you are seeing.
Sure - I get that. I have noticed, though, that if you're trying to include custom modules into core modules, you need to tell classes to re-include those modules anyway. I had a module Trackable mine that I wanted to include in module Enumerable core so I didn't have to explicitly include it in all of its including classes e. Patrick: Yes, include classes for all included mixins are created when the mixin is included in the class.
Adding a mixin after that will not create a new include class. Otherwise Ruby would have keep track of every class the mixin has ever been included in and update them whenever you include a new mixin. Or worse, if you were to get rid of include classes altogether, it would have to linearize the entire mixin chain on every method call. Find centralized, trusted content and collaborate around the technologies you use most. Connect and share knowledge within a single location that is structured and easy to search.
Possible Duplicate: What is the difference between include and extend in Ruby? Will foo be considered an instance method or a class method? In other words, is this equivalent to:. I wrote a blog posting about this a long time ago here. When you're "including" a module, the module is included as if the methods were defined at the class that's including them, you could say that it's copying the methods to the including class.
When you're "extending" a module, you're saying "add the methods of this module to this specific instance ".
When you're inside a class definition and say "extend" the "instance" is the class object itself, but you could also do something like this as in my blog post above :. So, it's not exactly a class method, but a method to the "instance" which you called "extend".
As you're doing it inside a class definition and the instance in there is the class itself, it "looks like" a class method. More generally, include only makes sense on a Class or Module , while extend can be used to add methods to any Object.
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