Ruby Define Constant Dynamically

Ruby contains a wide range of predefined variables.

Ruby define constant dynamically. The constant is looked up in the parent and its ancestors. They can only be defined outside of methods unless you use metaprogramming. Let s define parent to be that qualifying class or module object that is billing in the example above. It s not through hash it s array access operator.

For two of them i use attr reader. Myconstant hello hello unlike other programming languages ruby. The final way of defining a method dynamically in ruby is using def or define method. You cannot assign any value to these variables.

They are special variables that have the appearance of local variables but behave like constants. Apiobject subclasses match the object names from the api that i m p. The algorithm for qualified constants goes like this. Constants are used for values that aren t supposed to change but ruby doesn t prevent you from changing them.

Every predefined variable has its own specification. It will define a new method on the metaclass of the o local variable constant or result of method call. In ruby 2 5 object is skipped if present among the ancestors. You can use predefine variables to perform a specific task like when dealing with interpreter parameters or regular expressions.

Here var1 and var2 are constants. Using ruby i want to dynamically create class level instance variables inside corresponding getters. Def keys define here end def keys value define here end of course if you won t be using multiple keys to access an element you re fine with using just key instead of. A ruby constant is used to store a value for the duration of a ruby program s execution.

To implement it you need to define methods. A constant is a type of variable which always starts with a capital letter. This will produce the following result value of first constant is 100 value of second constant is 200 ruby pseudo variables. But for those which need to be initialized to an empty array i do the following.

Constants are declared by beginning the variable name with a capital letter a common convention for declaring constants is to use uppercase letters for the entire name. I have a class api that pulls objects from a third party api and builds them into objects that are subclasses of type apiobject.