Ruby Define Constant In Class

Although constants should not be changed you can modify the internal states of the objects they reference as seen in.

Ruby define constant in class. In ruby 1 9 this has been addressed by adding an optional parameter. The name should always be in initial capitals. Module constants all constants one argument. Usr bin ruby class example var1 100 var2 200 def show puts value of first constant is var1 puts value of second constant is var2 end end create objects object example new object show here var1 and var2 are constants.

Ruby performs a lookup for the constant that follows a class or module keyword because it needs to know if the class or module is going to be created or reopened. It is very important to understand that ruby does not have a way to truly reload classes and modules in memory and have that reflected everywhere they are already used. 6 1 1 constants after the class and module keywords. It never looks in subclass and so it can t find a definition for the constant.

If the constant is not defined at that point it is not considered to be a missing constant autoloading is not triggered. As you can see the class object stored in the user constant is different after reloading. Module constants true constants of module and. A method is a thing your class can do.

Here s a code example. Note that constants do not exist until a value is actually assigned to them. So just define your constants outside methods typically we want to have constant definitions at the top of your class so they are clearly visible. Your confusion is due to the fact that the class method module constants hides the instance method module constants for module.

When we call sub class instance foo via constant ruby searches for foo constant in myclass and its superclasses. So this is the way ruby s constant lookup algorithm works. Making ruby classes more useful. A class in ruby always starts with the keyword class followed by the name of the class.

You can squeeze an orange to get juice. 6 1 reloading and stale objects. This will produce the following result. Uses the instance method.

Classes become more useful when you start adding instance methods instance variables to them. Ruby class and module names are also constants but they are conventionally written using initial capital letters and camel case likethis. Same class method as in 1 8.