Binding Blocks? (in Tk, for example)

Ruby
1

So I was playing with ruby-tk and this syntax really suprised me:

TkLabel.new {
text “Hello, World”
pack …
}

‘text’ isn’t available outside the block, so I assume the function is
getting evaulated in TkLabel’s scope?

How does TkLabel pull the block into it’s internal scope?

Thanks,
Mat

2

“M” == Mat S. [email protected] writes:

M> How does TkLabel pull the block into it’s internal scope?

it use instance_eval

Guy Decoux

3

On May 26, 2006, at 9:40 AM, ts wrote:

“M” == Mat S. [email protected] writes:

M> How does TkLabel pull the block into it’s internal scope?

it use instance_eval

Can you give a code example or documentation page? I can’t figure
out how to use instance_eval with a Proc or yield…
-Mat

4

On May 26, 2006, at 9:52 AM, ts wrote:

“M” == Mat S. [email protected] writes:

M> Can you give a code example or documentation page?

[code ommited]

That example wasn’t quite what I meant, but I found it myself.
Incase anyone else was following and is interested, here’s the sort
of syntax I was curious about:

class MyClass
def initialize &block
instance_eval &block
end

def foo
puts “hi”
end
end

MyClass.new { foo }

Thanks for pointing me in the right direction, Guy.
-Mat

5

“M” == Mat S. [email protected] writes:

M> Can you give a code example or documentation page?

moulon% cat b.rb
#!/usr/bin/ruby
class TkLabel
def text(*args)
puts “text #{args}”
end

def pack(*args)
puts “pack #{args}”
end
end

TkLabel.new.instance_eval {
text(1, 2)
pack(3, 4)
}
moulon%

moulon% ./b.rb
text 12
pack 34
moulon%

Guy Decoux