CODEWITHSUNDEEP
ruby
user1466717
user1466717

Reputation: 789

Interested in what the "<<" does

Came across this code.

def setup(&block)
  @setups << block
end

What does this line do?

@setups << block

Interested in what the does "<<".

The manual says that it is the operator of double shift, but he is here with?

Upvotes: 4

Views: 666

Answers (3)

mikej
mikej

Reputation: 66263

For an array << is the append method. It adds an item to the end of the array.

So in your specific case when you call setup with a block the Proc object made from the block is stored in @setups.

Note: as sbeam points out in his comment, because << is a method, it can do different things depending on the type of object it is called on e.g. concatenation on strings, bit shifting on integers etc.

See the "ary << obj → ary" documentation.

Upvotes: 8

Jesper
Jesper

Reputation: 7605

<< in Ruby is commonly used to mean append - add to a list or concatenate to a string.

The reason Ruby uses this is unclear but may be because the library largely distinguishes between changing an object and returning a changed object (methods that change the objects tend to have a ! suffix). In this way, << is the change-the-object counterpart to +.

Upvotes: 1

Brian Agnew
Brian Agnew

Reputation: 272237

It's building an array by pushing elements onto the end of it.

Here's the manual entry.

Upvotes: 1

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