Get the value of an instance variable given its name
The most idiomatic way to achieve this is:
some_object.instance_variable_get("@#{name}")
There is no need to use +
or intern
; Ruby will handle this just fine. However, if you find yourself reaching into another object and pulling out its ivar, there's a reasonably good chance that you have broken encapsulation.
If you explicitly want to access an ivar, the right thing to do is to make it an accessor. Consider the following:
class Computer def new(cpus) @cpus = cpus endend
In this case, if you did Computer.new
, you would be forced to use instance_variable_get
to get at @cpus
. But if you're doing this, you probably mean for @cpus
to be public. What you should do is:
class Computer attr_reader :cpusend
Now you can do Computer.new(4).cpus
.
Note that you can reopen any existing class and make a private ivar into a reader. Since an accessor is just a method, you can do Computer.new(4).send(var_that_evaluates_to_cpus)
To get an instance variable from the name of an instance variable do:
name = "paramName"instance_variable_get(("@" + name).intern)
This will return the value of the instance variable @paramName