Extra information needed
Sometimes an object needs a little bit of extra information in order to do what you ask for.
For example the class
String defines the method
delete which returns
another String with some of the characters deleted. In order to do so, of
course, it needs to know which characters we’d like to remove.
We can pass things by appending parentheses
() to the method call (the name).
We can then include the extra bit of information needed (in our case another
string) inside the parentheses like so:
$ irb > name = "Ruby Monstas" > name.delete("by Mo") => "Runstas"
Hm. Not sure what “Runstas” means. Ideas? Let us know.
Anyhow, another example for a method that needs an argument is the method
prepend on Strings. This method returns a new String with the given String
> name = "Ruby Monstas" > name.prepend("Oh, hello, ") => "Oh, hello, Ruby Monstas"
These extra bits of information are called arguments. We’ll discuss them more once we get to define our own methods.
Not all methods need these extra bits of information (arguments) in order to do
their job. E.g. the method
length on Strings knows the length of their
String just so (because it knows its String). Sometimes they need one or more
So how do you know?
You might remember, over time, for some important methods, but most of us also check the documentation quite frequently, too. Some times it’s just fine to try it out quickly, and only check the documentation if it does not work as expected.