passing procs around in variables

[Nathan]

Hi,
This might be something really simple, but I'm trying to write a
console-based menu for my program. I've done this before in a
procedural language, but I decided to try and port what I've done to
ruby, because it'll make other parts of my program far easier. My
program has a few menus, so it'd be nice to have re-usable code (which
the procedural version didn't have much of).

The best way I've come up with is to pass the method calls which are
executed by each menu item as procs, but this requires passing them
around between two objects internally. (I haven't completely decided
how I'm going to structure the code which passes the procs... I have
an idea, but I'll cross that when I come to it)

Now, the Item class, which each menu item is an object of, doesn't
work as expected... take a look here: http://pastie.caboo.se/163781.
When I try to call myItem.execute!, it complains "no block given". If
I call myItem.execute! { 2 + 1}, then it works, but that's not what I
want...

I've also included the Menu class, just in case anybody has any advice
as to how to do the whole thing better.

Thanks,
-Nathan

 

[Stefan Lang]

[...]
Now, the Item class, which each menu item is an object of, doesn't
work as expected... take a look here: http://pastie.caboo.se/163781.
When I try to call myItem.execute!, it complains "no block given". If
I call myItem.execute! { 2 + 1}, then it works, but that's not what I
want...

class Item
attr_reader :text

def initialize(description, &proc)
@description = description
@proc = proc
end

def execute!
yield @proc
end
end

Use yield when the block is _not_ stored in a variable.
What your yield line does is this: Call the block given to
execute! with @proc as argument.

Once you have a proc object, you can call it, well, with
the "call" method. Just change "yield @proc" to
"@proc.call" and it should work.

HTH,
Stefan

 

[Nathan]

Thanks, that's great.

2008/3/9, Nathan <[email protected]>:

[...]
Now, the Item class, which each menu item is an object of, doesn't
work as expected... take a look here:http://pastie.caboo.se/163781.
When I try to call myItem.execute!, it complains "no block given". If
I call myItem.execute! { 2 + 1}, then it works, but that's not what I
want...
class Item
attr_reader :text

def initialize(description, &proc)
@description = description
@proc = proc
end

def execute!
yield @proc
end
end

Use yield when the block is _not_ stored in a variable.
What your yield line does is this: Call the block given to
execute! with @proc as argument.

Once you have a proc object, you can call it, well, with
the "call" method. Just change "yield @proc" to
"@proc.call" and it should work.

HTH,
Stefan

 

[Ken Bloom]

Hi,
This might be something really simple, but I'm trying to write a
console-based menu for my program. I've done this before in a procedural
language, but I decided to try and port what I've done to ruby, because
it'll make other parts of my program far easier. My program has a few
menus, so it'd be nice to have re-usable code (which the procedural
version didn't have much of).

The best way I've come up with is to pass the method calls which are
executed by each menu item as procs, but this requires passing them
around between two objects internally. (I haven't completely decided how
I'm going to structure the code which passes the procs... I have an
idea, but I'll cross that when I come to it)

Now, the Item class, which each menu item is an object of, doesn't work
as expected... take a look here: http://pastie.caboo.se/163781. When I
try to call myItem.execute!, it complains "no block given". If I call
myItem.execute! { 2 + 1}, then it works, but that's not what I want...

I've also included the Menu class, just in case anybody has any advice
as to how to do the whole thing better.

Thanks,
-Nathan

In addition to what Stefan Lang said about @proc.call, I just wanted to
point out that there's no need to keep different classes in different
files. (This isn't Java.)

--Ken

 

[Nathan]

Yeah, I know. I=B4m just doing it like that for now, then I=B4ll put them
all together at the end. Thanks though.
-N

In addition to what Stefan Lang said about @proc.call, I just wanted to
point out that there's no need to keep different classes in different
files. (This isn't Java.)

--Ken

w.iit.edu/~kbloom1/