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Ruby Ruby Foundations Hashes Creating Hashes

Posted by Sebastian Velandia
Sebastian Velandia
24,676 Points

is always necesary to use Hash.new {proc} when creating a proc?

Hello I see that when you want to create a proc you use this syntax

yourHash = Hash.new {|hash, key| hash[hey]= "some value for #{key}"}

but for example I now that you can create a hash just using the curly braces instead of use "Hash.new"

So my question is, if is possible to create a proc without to use "Hash.new"

I tried this but it did not work

yourHash = {|hash, key| hash[hey]= "some value for #{key}"}

Thanks

3 Answers

Ronald Jackson
Ronald Jackson
9,229 Points
Ronald Jackson
Ronald Jackson
9,229 Points

Hi Sabastian

In Ruby, you don't create a proc using Hash.new. You create a proc by calling Proc.new and passing a block. For example: myproc = Proc.new{}.

Alternate syntax allows you to create a proc by using the keyword proc and passing in a block. For example: myproc = proc{}

Hope this helps!

Best,

Ronald

Jessica Barnett
Jessica Barnett
8,028 Points
Jessica Barnett
Jessica Barnett
8,028 Points

This is more of an extended question than an answer....

How is it that you're able to create / use a proc by calling Hash.new {} then? Are the Hash and Proc objects related somehow?

Why is it that you're not able to do something like this:

my_hash = {} { |hash, key| hash[hey]= "some value for #{key}" }

If the {} and Hash.new do basically the same thing - return an empty hash - then why is the behavior different when you try to use a proc with them?

Ronald Jackson
Ronald Jackson
9,229 Points
Ronald Jackson
Ronald Jackson
9,229 Points

Jessica -

Check out this Stackoverflow.com thread about setting a hash's default_proc: http://stackoverflow.com/questions/20158213/ruby-hash-creating-a-default-value-for-non-existing-elements

Ronald