Ruby Cookbook

Recipe 8.1. Managing Instance Data Problem You want to associate a variable with an object. You may also want the variable to be readable or writable from outside the object. Solution Within the code for the object's class, define a ...

Recipe 8.2. Managing Class Data Problem Instead of storing a bit of data along with every instance of a class, you want to store a bit of data along with the class itself. Solution Instance variables are prefixed by a single ...

Recipe 8.3. Checking Class or Module Membership Problem You want to see if an object is of the right type for your purposes. Solution If you plan to call a specific method on the object, just check to see whether the object reponds t...

Recipe 8.4. Writing an Inherited Class Problem You want to create a new class that extends or modifies the behavior of an existing class. Solution If you're writing a new method that conceptually belongs in the original class, you ca...

Recipe 8.5. Overloading Methods Problem You want to create two different versions of a method with the same name: two methods that differ in the arguments they take. Solution A Ruby class can have only one method with a given name. W...

Recipe 8.6. Validating and Modifying Attribute Values Problem You want to let outside code set your objects' instance variables, but you also want to impose some control over the values your variables are set to. You might wan...

Recipe 8.7. Defining a Virtual Attribute Problem You want to create accessor methods for an attribute that isn't directly backed by any instance variable: it's a calculated value derived from one or more different instance variable...

Recipe 8.8. Delegating Method Calls to Another Object Problem You'd like to delegate some of an object's method calls to a different object, or make one object capable of " impersonating" another. Solution If you want to completely...

Recipe 8.9. Converting and Coercing Objects to Different Types Problem You have an object of one type and you want to use it as though it were of another type. Solution You might not have to do anything at all. Ruby doesn't enfo...

Recipe 8.10. Getting a Human-Readable Printout of Any Object Problem You want to look at a natural-looking rendition of a given object. Solution Use Object#inspect. Nearly all the time, this method will give you something more readable...

Recipe 8.11. Accepting or Passing a Variable Number of Arguments Problem You want to write a method that can accept any number of arguments. Or maybe you want to pass the contents of an array as arguments into such a method, rather than ...

Recipe 8.12. Simulating Keyword Arguments Problem A function or method can accept many optional arguments. You want to let callers pass in only the arguments they have values for, but Ruby doesn't support keyword arguments as Python and Li...

Recipe 8.13. Calling a Superclass's Method Problem When overriding a class's method in a subclass, you want to extend or decorate the behavior of the superclass, rather than totally replacing it. Solution Use the super keywor...

Recipe 8.14. Creating an Abstract Method Problem You want to define a method of a class, but leave it for subclasses to fill in the actual implementations. Solution Define the method normally, but have it do nothing except raise a ...

Recipe 8.15. Freezing an Object to Prevent Changes Problem You want to prevent any further changes to the state of an object. Solution Freeze the object with Object#freeze: frozen_string = 'Brrrr!' frozen_string.freeze frozen...

Recipe 8.16. Making a Copy of an Object Problem You want to make a copy of an existing object: a new object that can be modified separately from the original. Solution Ruby provides two ways of doing this. If you only want to have to reme...

Recipe 8.17. Declaring Constants Problem You want to prevent a variable from being assigned a different value after its initial definition. Solution Declare the variable as a constant. You can't absolutely prohibit the variable from ...

Recipe 8.18. Implementing Class and Singleton Methods Problem You want to associate a new method with a class (as opposed to the instances of that class), or with a particular object (as opposed to other instances of the same class). ...