Sorting different objects

rubyonrails-talk
1

hi

I have an array of topics and posts each has an updated_on field. I want to sort the array so in the order of the updated_on field.

I.e

1 Topic updated on 5 march 2 Poll updated on 4 march 3 Topic updated on 6 march 4 poll updated on 7 march

shoud go 4,3,1,2

my code looks like this @topicsAndPolls.sort { |a,b| a.updated_on <=> b.updated_on} but this isnt working. Do I have to define the <=> method somewhere. Can I pass that in the block aswell?

Thanks

Iain Adams

2

I have an array of topics and posts each has an updated_on field. I want to sort the array so in the order of the updated_on field.

        [...]

my code looks like this @topicsAndPolls.sort { |a,b| a.updated_on <=> b.updated_on} [\n inserted] but this isnt working. Do I have to define the <=> method somewhere. Can I pass

What do you assign the result of this to? Or did you mean   @topicsAndPolls.sort! { |a,b| a.updated_on <=> b.updated_on}

? That's s/sort/sort!/ in sed parlance, in case the addition of one char is as hard for you to spot as for me.

that in the block aswell?

If updated_on returns a Date then <=> should work. If it doesn't you'll get a NoMethodError.

        Hugh

3

I have an array of topics and posts each has an updated_on field. I want to sort the array so in the order of the updated_on field.

I.e

1 Topic updated on 5 march 2 Poll updated on 4 march 3 Topic updated on 6 march 4 poll updated on 7 march

shoud go 4,3,1,2

my code looks like this @topicsAndPolls.sort { |a,b| a.updated_on <=> b.updated_on} but this isnt working. Do I have to define the <=> method somewhere. Can I pass that in the block aswell?

In addition to the other reply, you're looking for a descendant sort... so you really want: { |a,b| b.updated_on <=> a.updated_on}

(not the switching of a and b)

-philip