How can I do this better?

[Sam Kong]

Hi,

I find myself to use the following idiom frequently.

def foo i
return @cache if @cache
@cache = some_method_that_takes_long_time(i)
end

I like the post-modifying if statement.
But I feel uncomfortable with calling @cache twice.

I wish this worked.
return v if v = @cache #=> undefined local variable or method `v'

This works but it's long.
if v = @cache
return v
end

Maybe this is a compromise.
if v = @cache then return v end

I want "return statement" to stand out.
Post-modification looks better for that.
So I call @cache twice.

How do you do it?

Sam

 

[Jean Helou]

def foo i
return @cache ? @cache : some_method_that_takes_long_time(i)
end

jean

 

[Jean Helou]

actually this seems to work too :
def foo(1)
@cache||=some_method_that_takes_long_time(i)
end

limited testing in a trivial case in for both

jean

def foo i
return @cache ? @cache : some_method_that_takes_long_time(i)
end

jean

Hi,

I find myself to use the following idiom frequently.

def foo i
return @cache if @cache
@cache = some_method_that_takes_long_time(i)
end

I like the post-modifying if statement.
But I feel uncomfortable with calling @cache twice.

I wish this worked.
return v if v = @cache #=> undefined local variable or method `v'

This works but it's long.
if v = @cache
return v
end

Maybe this is a compromise.
if v = @cache then return v end

I want "return statement" to stand out.
Post-modification looks better for that.
So I call @cache twice.

How do you do it?

Sam

 

[Robert Klemme]

actually this seems to work too :
def foo(1)

You want "def foo(i)" here.

@cache||=some_method_that_takes_long_time(i)
end

That's what I'd do. And then there is also memoize, which implements
this pattern:

http://raa.ruby-lang.org/project/memoize/

Kind regards

robert

 

[Simon Strandgaard]

I find myself to use the following idiom frequently.

def foo i
return @cache if @cache
@cache = some_method_that_takes_long_time(i)
end

I like the post-modifying if statement.
But I feel uncomfortable with calling @cache twice.

[snip]

how about?

irb(main):001:0> a = nil
=> nil
irb(main):002:0> a ||= 42
=> 42
irb(main):003:0> a ||= 666
=> 42
irb(main):004:0> a
=> 42

 

[Andrew Stewart]

I find myself to use the following idiom frequently.

def foo i
return @cache if @cache
@cache = some_method_that_takes_long_time(i)
end

You could also use the 'overlooked feature of Ruby hashes' and put
your lengthy method in the block you pass to Hash.new:

http://moonbase.rydia.net/mental/blog/programming/overlooked-feature-
of-ruby-hashes.html

Regards,
Andy Stewart

 

[Robert Klemme]

I find myself to use the following idiom frequently.

def foo i
return @cache if @cache
@cache = some_method_that_takes_long_time(i)
end

You could also use the 'overlooked feature of Ruby hashes' and put your
lengthy method in the block you pass to Hash.new:

http://moonbase.rydia.net/mental/blog/programming/overlooked-feature-of-ruby-hashes.html

That's definitively a better option - especially if i is non numeric.

def initialize
@foo = Hash.new {|h,k| h[k] = some_method_that_takes_long_time(k)}
end

def foo(i)
@foo
end

Cheers

robert

 

[Gregory Seidman]

On Fri, Jan 05, 2007 at 06:05:32PM +0900, Sam Kong wrote:
} Hi,
}
} I find myself to use the following idiom frequently.
}
} def foo i
} return @cache if @cache
} @cache = some_method_that_takes_long_time(i)
} end
[...]
} How do you do it?

You may find this of use:

http://redcorundum.blogspot.com/2006/09/simple-flyweight-implementation_26.html

} Sam
--Greg

 

[Sam Kong]

Hi gaurav,

hi,

def foo i

@cache||=some_method_that_takes_long_time(i)

end

This is great.
I'll use this pattern from now on.

Thanks.

Sam

 

[Sam Kong]

Hi Gregory,

You may find this of use:

http://redcorundum.blogspot.com/2006/09/simple-flyweight-implementation_26.html

Yes.
It's very interesting and useful.

Thanks.

Sam

 

[Sam Kong]

Hi Robert,

(1) some people wondered recently why "or" and "and" have such low a
precedence, I guess this example is a reason behind this.

Probably because ruby provides "||" and "&&" also for higher
precedence.

Thanks.
Sam

 

[Sam Kong]

I think so too, but just one worry, did you read me here?
Tthis was only a side remark but what I meant is

v = ... and return v # does what you want
v = ... && return v # is not even correct syntax

Cheers
R.

Of course, I read you.^^
That's a good suggestion.
@cache ||= some_method(i) kills all others, though.

Thanks.

Sam