Is there an opposite function of slice function in Ruby?

Question

In this post, slice function is used to get only necessary elements of params. What would be the function I should use to exclude an element of params (such as user_id)?

Article.new(params[:article].slice(:title, :body))

Thank you.

Erlandson

Answer 1

Use except:

a = {"foo" => 0, "bar" => 42, "baz" => 1024 }
a.except("foo")
# returns => {"bar" => 42, "baz" => 1024}

Stay

It's worth noting that except is a method that is added by Rails and is not normally available if working with Ruby by itself – Marti

Ruby 3 has added except to Hash. See docs here – Wakashan

also observe that, in Rails, the mutating version of the method, except! returns the same as except, while it must probably rather return the excluded part (just to be aligned with its counterpart method, slice!. Maybe something to raise up with the Rails team. – Mog

Answer 2

Inspired in the sourcecode of except in Rails' ActiveSupport

You can do the same without requiring active_support/core_ext/hash/except

# h.slice( * h.keys - [k1, k2...] )

# Example:
h = { a: 1, b: 2, c: 3, d: 4 }
h.slice( * h.keys - [:b, :c] ) # => { a: 1, d: 4}

Note: Ruby 3+ Hash incorporated this except method:

# Ruby 3+
h.except(:b, :c) # => { a: 1, d: 4}

Clone

I knew there should be some nifty trick, although using Ruby 3+ doesn't require it. – Bussard

@akostadinov, thanks for the tip. I'll add a note about Ruby 3+. – Clone

Answer 3

Considering only standard Ruby.

For Ruby versions below 3, no.

For Ruby 3, yes. You can use except.

Odiliaodille

Answer 4

Try this

params = { :title => "title", :other => "other", :body => "body"  }

params.select {|k,v| [:title, :body].include? k  } #=> {:title => "title", :body => "body"}  

Lipoprotein

at least it's Ruby. To be fair, slice and except are both Rails methods. – Sire

Slice is Ruby, for the rest you are right. – Sommer