Question about exiting from a block

ruby-talk
1

def test
  puts 'before'
  yield 2
  puts 'after'
end

test do |i|
  XXX if i > 1
  # a lot of code appears below
end

I have code above and wonder if it is possible to use
return/break/anything to stop execution of block and return control to
test() to execute code after yield. I know it is impossible in 1.8. How
about 1.9? Does anyone feel this is an important feature to have?

Thank you.
Guoliang Cao

···

--
Posted via http://www.ruby-forum.com/.

2

Guoliang Cao wrote:

def test
  puts 'before'
  yield 2
  puts 'after'
end

test do |i|
  XXX if i > 1
  # a lot of code appears below
end

I have code above and wonder if it is possible to use
return/break/anything to stop execution of block and return control to
test() to execute code after yield. I know it is impossible in 1.8. How
about 1.9? Does anyone feel this is an important feature to have?

It is possible in 1.8, using the next keyword:

def test
   puts 'before'
   yield 2
   puts 'after'
end

test do |i|
   next if i > 1
   puts "a lot of code"
end

···

--
       vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407

3

Why is it impossible? Doesn't "break" do what you need? (And remember,
"break" and "next" can even return a value from a block to the yielder.)
m.

···

Guoliang Cao <gcao@vonage.com> wrote:

def test
  puts 'before'
  yield 2
  puts 'after'
end

test do |i|
  XXX if i > 1
  # a lot of code appears below
end

I have code above and wonder if it is possible to use
return/break/anything to stop execution of block and return control to
test() to execute code after yield. I know it is impossible in 1.8.

--
matt neuburg, phd = matt@tidbits.com, Matt Neuburg’s Home Page
Leopard - http://www.takecontrolbooks.com/leopard-customizing.html
AppleScript - http://www.amazon.com/gp/product/0596102119
Read TidBITS! It's free and smart. http://www.tidbits.com

4

Keeping it simple:

def test
  puts 'before'
  yield 2
  puts 'after'
end

test do |i|
  unless i > 1
    puts "a lot of code here"
  end
end

There's also throw/catch:

test do |i|
  catch(:done) do
    throw(:done) if i > 1
    puts "a lot of code here"
  end
end

···

--
Posted via http://www.ruby-forum.com/.

5

matt neuburg wrote:

···

Guoliang Cao <gcao@vonage.com> wrote:

def test
  puts 'before'
  yield 2
  puts 'after'
end

test do |i|
  XXX if i > 1
  # a lot of code appears below
end

I have code above and wonder if it is possible to use
return/break/anything to stop execution of block and return control to
test() to execute code after yield. I know it is impossible in 1.8.

Why is it impossible? Doesn't "break" do what you need? (And remember,
"break" and "next" can even return a value from a block to the yielder.)

Nope, break will skip the "after" line.

--
       vjoel : Joel VanderWerf : path berkeley edu : 510 665 3407

6

Joel VanderWerf wrote:

Guoliang Cao wrote:

I have code above and wonder if it is possible to use
return/break/anything to stop execution of block and return control to
test() to execute code after yield. I know it is impossible in 1.8. How
about 1.9? Does anyone feel this is an important feature to have?

It is possible in 1.8, using the next keyword:

def test
   puts 'before'
   yield 2
   puts 'after'
end

test do |i|
   next if i > 1
   puts "a lot of code"
end

This is great! I never thought of using 'next'.

Thank you!

···

--
Posted via http://www.ruby-forum.com/\.

7

Hi,

Guoliang Cao wrote:

I have code above and wonder if it is possible to use
return/break/anything to stop execution of block and return control to
test() to execute code after yield. I know it is impossible in 1.8. How
about 1.9?

It is possible in 1.8, using the next keyword:

Slightly modified:

  def f ; puts "A" ; puts yield ; puts "Z" ; "F" ; end

  f { next "X" ; puts "Y" } #=> "F"
  puts "-"
  f { break "X" ; puts "Y" } #=> "X"

The output is:

  A
  X
  Z

···

Am Freitag, 05. Jun 2009, 06:48:43 +0900 schrieb Joel VanderWerf:
  -
  A

Will this work in 1.9, too?

Bertram

--
Bertram Scharpf
Stuttgart, Deutschland/Germany
http://www.bertram-scharpf.de

8

Right, sorry about that. m.

···

Joel VanderWerf <vjoel@path.berkeley.edu> wrote:

matt neuburg wrote:
> Guoliang Cao <gcao@vonage.com> wrote:
>
>> def test
>> puts 'before'
>> yield 2
>> puts 'after'
>> end
>>
>> test do |i|
>> XXX if i > 1
>> # a lot of code appears below
>> end
>>
>>
>> I have code above and wonder if it is possible to use
>> return/break/anything to stop execution of block and return control to
>> test() to execute code after yield. I know it is impossible in 1.8.
>
> Why is it impossible? Doesn't "break" do what you need? (And remember,
> "break" and "next" can even return a value from a block to the yielder.)

Nope, break will skip the "after" line.

--
matt neuburg, phd = matt@tidbits.com, Matt Neuburg’s Home Page
Leopard - http://www.takecontrolbooks.com/leopard-customizing.html
AppleScript - http://www.amazon.com/gp/product/0596102119
Read TidBITS! It's free and smart. http://www.tidbits.com