how to tap in ruby

Ruby has an interesting and useful method called tap. Its defined in object.c so available wherever you desire for it it be.

Its function is simple. When called upon an object with a proc as a paramter, it calls the passed in proc with the object as a parameter and then it returns the objcet.

VALUE
rb_obj_tap(VALUE obj)
{
    rb_yield(obj);
    return obj;
}

Here is one use case

User.first.tap { |u| puts u.id}.update_attributes :name => "x"

This will print the user id and then pass on the user object to the nex chained thing.

Here is another more useful example

User.first.tap { |u| u.name = "Sample Person" }.email_sample_report

Here we changed the name of the user for the purpose of sending out a sample report. the name gets changed on the object which was tapped, then that object gets passed on to the next chained method which emails a report which uses the name.

From the DOC

Yields x to the block, and then returns x. The primary purpose of this method is to “tap into” a method chain, in order to perform operations on intermediate results within the chain.