Ruby variable scope blocks

Question

In C you can use statement blocks to isolate local variables from its parent scope.

int foo() {
    {
        int a;
    }
    // Here `a` is no longer in the scope.
}

But in Ruby the following fails to parse.

def foo
    do
        a = 1
    end
    puts a
end

Is there a trick to isolate variables into a scope in Ruby?

The notation for declaring an inline block is begin ... end, not do ... end. — tadman
– tadman, Commented Oct 8, 2014 at 20:28
In Ruby scope gates are created by 3 keywords.. def, class and module. — Arup Rakshit
– Arup Rakshit, Commented Oct 8, 2014 at 20:31
@tadman begin; a = 1; end; puts a prints 1, so a is not confined to the scope of the begin block. — Vortico
– Vortico, Commented Oct 9, 2014 at 0:07

D-side · Accepted Answer · 2014-10-08 20:39:57Z

3

The most appropriate "inner scope" in most cases is a separate method. Usually, if some of the data during a certain block of algorithm should not be visible outside, it's worth extracting this block into a separate method. And it could as well be, that this block could make a nice argument.

As the docs state, these are all the cases that have their own local variable scope:

proc{ ... } (and, consequently, blocks in method calls)
loop{ ... } (a method that accepts a block, same as above)
def ... end (a method implementation)
class ... end
module ... end
the entire program (this is of no use in scope of the question though)

answered Oct 8, 2014 at 20:39

D-side

9,5353 gold badges31 silver badges47 bronze badges

Sign up to request clarification or add additional context in comments.

Comments

Vortico · Accepted Answer · 2014-10-08 20:18:32Z

2

The following works, but I suspect there are other ways.

proc {
    a = 5
}.call

answered Oct 8, 2014 at 20:18

Vortico

2,8794 gold badges34 silver badges53 bronze badges

Collectives™ on Stack Overflow

Ruby variable scope blocks

2 Answers 2

Comments

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

Comments

Comments

Your Answer

Sign up or log in

Post as a guest

Related