block_given? problem

[westlin9]

I can't figure out why the do...end block isn't detected by the
"block_given?" function. The problem occurs when a method call with a
block is used in a puts statement. See the code example below.
Can some one explain this to me please? Is this a bug?


class TheClass
def self.TheMethod()
if block_given?
puts "yes, block given"
else
puts "no block is given"
end
'return val'
end
end

# ok
puts TheClass.TheMethod {|param| 123}

# block not detected
puts TheClass.TheMethod do |param|
123
end

# ok
a = TheClass.TheMethod {|param| 123}
puts a

# ok
a = TheClass.TheMethod do |param|
123
end
puts a

 

[Robert Dober]

I can't figure out why the do...end block isn't detected by the
"block_given?" function. The problem occurs when a method call with a
block is used in a puts statement. See the code example below.
Can some one explain this to me please? Is this a bug?


class TheClass
def self.TheMethod()
if block_given?
puts "yes, block given"
else
puts "no block is given"
end
'return val'
end
end

# ok
puts TheClass.TheMethod {|param| 123}

# block not detected
puts TheClass.TheMethod do |param|
123
end

# ok
a = TheClass.TheMethod {|param| 123}
puts a

# ok
a = TheClass.TheMethod do |param|
123
end
puts a

puts( TheClass.TheMethod do nil end )

do...end and {} do not have the same precedence, thus, without the ()
you are doing this
puts( TheClass.TheMethod ) do nil end

HTH
Robert

 

[westlin9]

puts( TheClass.TheMethod do nil end )

do...end and {} do not have the same precedence, thus, without the ()
you are doing this
puts( TheClass.TheMethod ) do nil end

HTH
Robert

--
I always knew that one day Smalltalk would replace Java.
I just didn't know it would be called Ruby
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- Visa citerad text -

Thanks

 

[Mariusz Pękala]

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I can't figure out why the do...end block isn't detected by the
"block_given?" function. The problem occurs when a method call with a
block is used in a puts statement. See the code example below.
Can some one explain this to me please? Is this a bug?
=20
=20
class TheClass
def self.TheMethod()
if block_given?
puts "yes, block given"
else
puts "no block is given"
end
'return val'
end
end
=20
# ok
puts TheClass.TheMethod {|param| 123}
=20
# block not detected
puts TheClass.TheMethod do |param|
123
end

This is because do..end block gets attached to the 'puts' instead of
TheMethod.

do..end and {||..} differ in precedence. {||..} binds to the rightmost
method, while do..end to the leftmost one.

# ok
a =3D TheClass.TheMethod {|param| 123}
puts a
=20
# ok
a =3D TheClass.TheMethod do |param|
123
end
puts a

There you have no ambiguity as there is only one method call.


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[Rick DeNatale]

do...end and {} do not have the same precedence, thus, without the ()
you are doing this
puts( TheClass.TheMethod ) do nil end

do..end vs {}
and vs. &&
or vs. ||
not vs !

I think that it can be said that generally in ruby "symbols bind
tighter than words"