Newbie : assign a value to a variable...

[Nicolas Blanco]

Hi all!

This is really a newbie question...

Here is the simple code...

if @params[er_page].nil?
per_page = 20
else
per_page = @params[er_page]
end

Is there a better way to do this (put the parameter in the variable if
the parameter is not null, otherwise put 20) ?

Thanks...

Nicolas

 

[dblack]

Hi --

Hi all!

This is really a newbie question...

Here is the simple code...

if @params[er_page].nil?
per_page = 20
else
per_page = @params[er_page]
end

Is there a better way to do this (put the parameter in the variable if
the parameter is not null, otherwise put 20) ?

You can use the || (or) operator:

per_page = @params[er_page] || 20


David

--
http://www.rubypowerandlight.com => Ruby/Rails training & consultancy
----> SEE SPECIAL DEAL FOR RUBY/RAILS USERS GROUPS! <-----
http://dablog.rubypal.com => D[avid ]A[. ]B[lack's][ Web]log
http://www.manning.com/black => book, Ruby for Rails
http://www.rubycentral.org => Ruby Central, Inc.

 

[maikonaraujo]

Try this:

per_page = @params[er_page] || 20

Best Regards
Maikon Araujo.

 

[ChrisH]

Nicolas Blanco wrote:
....

if @params[er_page].nil?
per_page = 20
else
per_page = @params[er_page]
end

Is there a better way to do this (put the parameter in the variable if
the parameter is not null, otherwise put 20) ?

The usual idiom is
per_page = @params[er_page] || 20

cheers

 

[Harold Hausman]

Hi all!

This is really a newbie question...

Here is the simple code...

if @params[er_page].nil?
per_page = 20
else
per_page = @params[er_page]
end

Is there a better way to do this (put the parameter in the variable if
the parameter is not null, otherwise put 20) ?

#untested:
per_page = (@params[er_page] or 20)
#The theory is that if @params[er_page] is nil, it'll return false,
and the 'or' will kick in.

Thanks...

You're welcome.

Nicolas

hmmm,
-Harold

 

[Harold Hausman]

You can use the || (or) operator:

per_page = @params[er_page] || 20


David

I think you've got to be careful about your precedence there...

irb(main):001:0> foo = nil or 20
=> 20
irb(main):002:0> foo
=> nil
irb(main):003:0> foo = (nil or 20)
=> 20
irb(main):004:0> foo
=> 20

Though, maybe it's just irb?

-Harold

 

[James Edward Gray II]

You can use the || (or) operator:

per_page = @params[er_page] || 20


David

I think you've got to be careful about your precedence there...

irb(main):001:0> foo = nil or 20
=> 20
irb(main):002:0> foo
=> nil
irb(main):003:0> foo = (nil or 20)
=> 20
irb(main):004:0> foo
=> 20

Though, maybe it's just irb?

IRb and Ruby treat this the same, but David didn't use "or" so the
precedence is fine.

James Edward Gray II

 

[Harold Hausman]

You can use the || (or) operator:

per_page = @params[er_page] || 20


David

I think you've got to be careful about your precedence there...

irb(main):001:0> foo = nil or 20
=> 20
irb(main):002:0> foo
=> nil
irb(main):003:0> foo = (nil or 20)
=> 20
irb(main):004:0> foo
=> 20

Though, maybe it's just irb?

IRb and Ruby treat this the same, but David didn't use "or" so the
precedence is fine.

James Edward Gray II

holycrap.

Not to highjack this thread or anything, but what's the difference
between '||' and 'or' ?

Only precedence? Or is 'or' some kind of tricky method?

At least we both gave him working code, I guess... haha.

-Harold

 

[dblack]

Hi --

You can use the || (or) operator:

per_page = @params[er_page] || 20


David

I think you've got to be careful about your precedence there...

irb(main):001:0> foo = nil or 20
=> 20
irb(main):002:0> foo
=> nil
irb(main):003:0> foo = (nil or 20)
=> 20
irb(main):004:0> foo
=> 20

Though, maybe it's just irb?

No, it's just "or", which I didn't use. (Look more closely at my code



David

--
http://www.rubypowerandlight.com => Ruby/Rails training & consultancy
----> SEE SPECIAL DEAL FOR RUBY/RAILS USERS GROUPS! <-----
http://dablog.rubypal.com => D[avid ]A[. ]B[lack's][ Web]log
http://www.manning.com/black => book, Ruby for Rails
http://www.rubycentral.org => Ruby Central, Inc.

 

[Nicolas Blanco]

Thanks for the trick.

But the next problem is that if params[er_page] equals 0 then per_page
equals 0 and I get the error message "must have at least one item per
page" from the Rails paginate option...

Hi --

end

Is there a better way to do this (put the parameter in the variable if
the parameter is not null, otherwise put 20) ?

You can use the || (or) operator:

per_page = @params[er_page] || 20


David

 

[dblack]

Hi --

You can use the || (or) operator:

per_page = @params[er_page] || 20


David


I think you've got to be careful about your precedence there...

irb(main):001:0> foo = nil or 20
=> 20
irb(main):002:0> foo
=> nil
irb(main):003:0> foo = (nil or 20)
=> 20
irb(main):004:0> foo
=> 20

Though, maybe it's just irb?

IRb and Ruby treat this the same, but David didn't use "or" so the
precedence is fine.

James Edward Gray II

holycrap.

Not to highjack this thread or anything, but what's the difference
between '||' and 'or' ?

Only precedence? Or is 'or' some kind of tricky method?

Only precedence, as far as I know.


David

--
http://www.rubypowerandlight.com => Ruby/Rails training & consultancy
----> SEE SPECIAL DEAL FOR RUBY/RAILS USERS GROUPS! <-----
http://dablog.rubypal.com => D[avid ]A[. ]B[lack's][ Web]log
http://www.manning.com/black => book, Ruby for Rails
http://www.rubycentral.org => Ruby Central, Inc.

 

[James Edward Gray II]

Not to highjack this thread or anything, but what's the difference
between '||' and 'or' ?

"and" and "or" have much lower precedence than "&&" and "||", mostly
to allow for natural language constructs like:

res = may_return_nil() or raise "Oops, we got a nil!"

Hope that helps.

James Edward Gray II

 

[khaines]

Thanks for the trick.

But the next problem is that if params[er_page] equals 0 then per_page
equals 0 and I get the error message "must have at least one item per
page" from the Rails paginate option...

per_page = @params[er_page] || 20

In that case, use the trinary operator. Call to_i on @params[er_page]
if it could be nil, as you don't want to do that comparison with nil.

per_page = @params[er_page].to_i > 0 ? @params[er_page] : 20


Kirk Haines

 

[Jan Svitok]

Thanks for the trick.

But the next problem is that if params[er_page] equals 0 then per_page
equals 0 and I get the error message "must have at least one item per
page" from the Rails paginate option...

per_page = @params[er_page] || 20 # default
per_page = 20 if per_page <= 0 # validity check

or the other way round:

per_page = @params[er_page] # assignment
per_page = nil if per_page <= 0 # validity check
per_page ||= 20 # default

Choose what you like best.

 

[Nicolas Blanco]

Thanks!

I tried :
per_page = @params[er_page].to_i > 0 ? @params[er_page] : 20

but in this case if @params[er_page] = 'blahblah' it works, I get 20
in per_page but if @params[er_page] = 6 or another integer I get :
undefined method `>' for false:FalseClass

from Rails...

Nicolas.

Thanks for the trick.

But the next problem is that if params[er_page] equals 0 then per_page
equals 0 and I get the error message "must have at least one item per
page" from the Rails paginate option...

per_page = @params[er_page] || 20

In that case, use the trinary operator. Call to_i on @params[er_page]
if it could be nil, as you don't want to do that comparison with nil.

per_page = @params[er_page].to_i > 0 ? @params[er_page] : 20


Kirk Haines

 

[Luc Heinrich]

The usual idiom is
per_page =3D @params[er_page] || 20

You can also do:
per_page =3D @params.fetchper_page, 20)

Or:
@params.default =3D 20
per_page =3D @params[er_page]

--=20
Luc Heinrich - (e-mail address removed) - http://www.honk-honk.com

 

[gwtmp01]

You can also do:
per_page = @params.fetchper_page, 20)

Thanks for that. I've been oblivious to the default and block
options for fetch!


Gary Wright

 

[khaines]

I tried :
per_page = @params[er_page].to_i > 0 ? @params[er_page] : 20

but in this case if @params[er_page] = 'blahblah' it works, I get 20
in per_page but if @params[er_page] = 6 or another integer I get :
undefined method `>' for false:FalseClass

from Rails...

???

Can someone tell me what horrible thing Rails is doing to the language,
there?

How is @params[er_page].to_i becoming false?


Kirk Haines

 

[David Vallner]

Nicolas Blanco wrote

Is there a better way to do this (put the parameter in the variable if
the parameter is not null, otherwise put 20) ?

The original way works.

Just how much "better" than "works" do you want? I'd say fight the urges
to golf.

David Vallner

 

[Nicolas Blanco]

Thank you very much for all your answers...

I think I will use this for now :

per_page = @params.fetchper_page, 20).to_i
per_page = 20 if per_page <= 0

Nicolas.