i = 0 while i < 10 _i = i spawn do puts(_i) # <= the variable _i is not a shared variable, right? end i += 1 end Fiber.yield On my laptop, the output is: ╰─ $ 1 cr 1.cr 9 9 9 9 9 9 9 9 9 9

A block creates a new scope, so this program would have the desired effect: 10.times do |i| _i = i spawn do puts(_i) end end Fiber.yield EDIT: I removed an completely unnecessary begin ... end block which wasn’t supposed to be in the example.

That’s why you can also do spawn puts(i) It does all the boilerplate that @straight-shoota just typed.

There’s also a section in the reference book that I linked to that explains/suggests using spawn puts(i). Tho it seems my link gets collapsed down to make it look like i’m just linking to the concurrency docs suggesting “go look it up yourself” :sweat_smile:.

Thanks, @Blacksmoke16 , in fact, I have read these documents before. what i expected answer is @straight-shoota 's this answer, it made me understand why. i just remember that in some languages, golang? when assign the loop pushed variable into a local variable, can avoid this issue, that is way …

Actually Go has the same issue: redefining for loop variable semantics · Discussion #56010 · golang/go · GitHub

With a block you don’t need to assign the variable to another variable. That’s another advantage of blocks. No need for that _i in your example. I guess another advise is: try to use idiomatic code like looping over ranges, 10.times, etc. Try to avoid while, especially because there are many abstra…

Yes, in fact, following code works. 10.times do |i| spawn do puts(i) end end Fiber.yield But, following code not work. because begin ... end not create a new scope too. i = 0 while i < 10 begin _i = i spawn do puts(_i) end i += 1 end end Fiber.yield

Why pass variable into fiber(spawn) in a loop not work?

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straight-shoota November 5, 2022, 4:11pm 3

while does not create a new scope. So _i is closured and shared within the entire top-level scope.

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Why pass variable into fiber(spawn) in a loop not work?

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