How do I used matched arguments in elixir functions

问题

Say I have two use cases for a function. Do something with users that have a subscription and something with users that don't have a subscriptions.

def add_subscription(subscription_id, %User{subscription: nil})
  # Do something with user here.

And

def add_subscription(subscription_id, user)

How do I do pattern matching like this and also still use the user in the first function?

Thanks!

回答1:

You can bind the function argument to a variable:

def add_subscription(subscription_id, %User{subscription: nil} = user)

The convention is to assign after the pattern match:

# Do This
def foo(%User{subscription: nil} = user)

# Instead of this
def foo(user = %User{subscription: nil})

来源：https://stackoverflow.com/questions/36184062/how-do-i-used-matched-arguments-in-elixir-functions