advantage of tap method in ruby

Question

I was just reading a blog article and noticed that the author used tap in a snippet something like:

user = User.new.tap do |u|
  u.username = \         


        

Answer 1

I will give another example which I have used. I have a method user_params which returns the params needed to save for the user (this is a Rails project)

def user_params
  params.require(:user).permit(
    :first_name,
    :last_name,
    :email,
    :address_attributes
  )
end

You can see I dont return anything but ruby return the output of the last line.

Then, after sometime, I needed to add a new attribute conditionally. So, I changed it to something like this:

def user_params 
  u_params = params.require(:user).permit(
    :first_name, 
    :last_name, 
    :email,
    :address_attributes
  )
  u_params[:time_zone] = address_timezone if u_params[:address_attributes]
  u_params
end

Here we can use tap to remove the local variable and remove the return:

def user_params 
  params.require(:user).permit(
    :first_name, 
    :last_name, 
    :email,
    :address_attributes
  ).tap do |u_params|
    u_params[:time_zone] = address_timezone if u_params[:address_attributes]
  end
end