What are the differences between functions and methods in Swift?

Question

I always thought functions and methods were the same, until I was learning Swift through the \"Swift Programming Language\" eBook. I found out that I cannot use greet(

Answer 1

functional principle as a part of functional language

function is a first-class type (first-class citizen) in Swift

• assign to a variable
• pass as an argument
• return

Function

Function is a block of code that is created for executing some task. Function consists of name, optional parameters(name, type), optional return type, body.

func name(parameterName1: Int, parameterName2: String) -> Bool {
    //statements
    return true
}

Function type - function’s parameter type and return type

//Function type for the sample above
(Int, String) -> Bool

Method

Method - is a function which is associated with a type - class, structure, enum [About]:

Instance method - method which belongs to instance

MyClass().foo()

Type method - method which belongs to type itself. class or static is used[About]

MyClass.foo()

Closure

Closure - is a block of functionality. It is a function which supports capturing concept. It is similar to block in Objective-C. Also you can find that Closure is a Lambda in functionality world but lambda just a no-name function while Closure make a copies of non-local variable

Closure in Swift has three next forms:

• global function(with name, without capturing) - is a function that is declared in a global scope(out of class scope). Usually it is defined as a first level of .swift file and does not have a big memory food print
• nested function(with name, with capturing enclosing function variables) - function inside other function
• closure expression(without name, with capturing enclosing context)

{ () ->  in
      //body
}

[non-escaping vs @escaping closure]
[@autoclosure]