Swift - Function vs Method

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In Swift, functions and methods both are fundamental building blocks for optimizing and encapsulating code. It might be confusing to understand the difference between function and method, but we might think they are both the same. That's not true. The methods are used in class, struct, and enum.

They are called on the instances of that type and access and modify the properties of the instance. Whereas functions are defined independently or globally without creating a class or structure. Or we can say that a method is a function while a function is not a method.

Swift Functions

Functions are used to perform specific actions and are called by their names. It is very simple to pass the variables or constants as an argument while calling a function. Also, we can return a value from a function of any type. A function that works independently of a file can also be defined outside of it.

Syntax

Following is the syntax of a function −

func functionName(parameters...) -> returnType {
   //Write statements here to perform actions
}

Example

Swift program to demonstrate how to create and call a function.

// Function without return value
func show(msg: String) {
   print("Welcome to, \(msg)!")
}

// Function call
show(msg: "Tutorials Point")

// Function with return value
func sumOfNumbers(_ nums: [Int]) -> Int {
   var sum = 0

   // Calculating the sum of the numbers present in the array
   for n in nums {
      sum += n
   }
   return sum
}

// Function call with return value
let inputNumbers = sumOfNumbers([3, 5, 6, 7, 1]) 
print("Sum = \(inputNumbers)")

Output

It will produce the following output −

Welcome to, Tutorials Point!
Sum = 22

Swift Methods

A method is a function and can be defined in classes, structures, and enumerations. Using methods, we can perform certain actions according to your requirements. As per our needs, we can define more than one method to perform different tasks.

To access the defined methods in a class or structure we have to create an instance of the associated type. Using that object, we can call methods to perform tasks. Just like functions, we can also pass arguments while calling the method. Always remember that without creating an object of that class or struct we cannot access the methods.

In the Swift language, there are two types of methods like the following −

• Instance Methods − As per their names, these are the instance-specific methods that can be called through the instances. The compiler will give us an error if we will try to access the methods without an instance of that class or struct. Also, we cannot call the methods of a class (for eg. Class Student) from another class's instance.

• Type Methods − In Swift, we can define the type methods with prefix keywords like static or class. There is no need to create an instance of a class or struct to call type methods. They can be called directly from the type name.

Syntax

Following is the syntax of a method −

func methodName(parameters...) -> returnType {
   //Write statements here to perform actions
}

Example

Swift program to demonstrate how to create and call a method.

// Defining a structure 
struct Student {
    
   // Properties 
   let name: String
   let grade: Int
    
   // Instance method
   func displayInfo() {
      print("name: \(name)")
      print("grade: \(grade)")
   }
    
   // Type method
   static func dummyStudents() -> [Student] {
      return [Student(name: "Ray Sin", grade: 4),
      Student(name: "Cherry Blossom", grade: 2),
      Student(name: "Perry Scope", grade: 7)]
   }
}

// Creating instance of the structure
let anne = Student(name: "Anne Teak", grade: 5)

// Calling instance method from object anne
anne.displayInfo()

// Calling type method
let students = Student.dummyStudents()
print("number of students: ", students.count)

Output

It will produce the following output −

name: Anne Teak
grade: 5
number of students:  3

Visual Identification Between Function and Method

The Swift language shows how a function and method are denoted. It is visible that both are denoted as follows −

• The function has an icon like ƒ.

• The method has an icon of M.

Difference Between Methods and Functions in Swift

The following table will show the major difference between the methods and functions in Swift −