ruby on rails parsing variable to function-CodePudding

Can someone tell me difference between theese two code examples? What changes when putting ":" at the end of variable name?

def initialize(email:)
  @email = email
end

def initialize(email)
 @email = email
end

CodePudding user response：

email: in the method definition argument means that the method will be expecting a key-value pair as the method arguments. Sample initialization call:

YourClass.new(email: email_param)

while a simple email in the method definition argument means that the method will assign the passed argument to the variable email. Sample initialization call:

YourClass.new(email_param)

CodePudding user response：

email: is keyword argument

Keyword arguments follow any positional arguments and are separated by commas like positional arguments. You must use Kwarg can use default value

It work this way:

def my_method(arg1:, arg2: "default", arg3:)
  puts "arg1: #{arg1}, arg2: #{arg2}, arg3: #{arg3}"
end

my_method(arg3: 3, arg1: 1)
# will print arg1: 1, arg2: default, arg3: 3

my_method(arg2: 2, arg1: 1, arg3: 3)
# will print arg1: 1, arg2: 2, arg3: 3

my_method(arg2: 2)
# will raise ArgumentError (missing keywords: arg1, arg3)

Arguments order is important if these arguments are not keyword

def my_method(arg1, arg2 = "default", arg3)
  puts "arg1: #{arg1}, arg2: #{arg2}, arg3: #{arg3}"
end

my_method(1, 3)
# will print arg1: 1, arg2: default, arg3: 3

my_method(1, 2, 3)
# will print arg1: 1, arg2: 2, arg3: 3

my_method(1)
# will raise ArgumentError (wrong number of arguments (given 1, expected 2..3))