Feature #7432

Explicit way to define local variable in scope

Added by Ilya Vorontsov about 4 years ago. Updated about 4 years ago.

Target version:


Imagine code such as this
def test_smth
result = nil
assert_nothing_raised { result = some_slow_calculation }
assert_equal expected_answer, result
Line result = nil means nothing more than our intention to simply bind variable result in scope of assertion block with outer local variable. In large methods it can be much heavier to find out this obscured intention.
It may be better to introduce a method (if it can be implemented) or a keyword which simply creates a local variable (probably with nil value just to mark its existence)

define_variable 'x' or (define_variable x if it's a keyword)


#1 [ruby-core:50071] Updated by Charlie Somerville about 4 years ago

This should definitely not be a method, however I would welcome a 'local' keyword for this purpose.

#2 [ruby-core:50072] Updated by Yusuke Endoh about 4 years ago

  • Assignee set to Yukihiro Matsumoto
  • Priority changed from Normal to 3
  • Target version set to Next Major
  • Status changed from Open to Assigned

Assigning to matz, but don't hold your breath; matz has rejected such a explicit variable declaration syntax many times.

Yusuke Endoh

#3 [ruby-core:50073] Updated by Thomas Sawyer about 4 years ago

I have always been curious why there is no dynamic way to create local variables (other then eval).

Eg. x = 10 might be dynamically written:

local :x, 10

Since we can create just about anything else dynamically, it seems like stark omission.

#4 [ruby-core:50076] Updated by Yukihiro Matsumoto about 4 years ago

  • Status changed from Assigned to Rejected

Since I am sick of 'var' and 'local' in other languages, I don't want to add explicit local variable declaration, that requires a new keyword. Introducing a new keyword may break existing programs.

@trans Your idea would eliminate many chances to optimize.


#5 [ruby-core:50078] Updated by Thomas Sawyer about 4 years ago

I see why then. Thanks.

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