README.md

Protocols 1 ~ 12

1) What is Protocol? What kind of methods the protocol contains?

Answer:

• Protocol is a set of Property and Method declarations which are expected to be implemented in the adopting class.

2) Can we define methods in Protocol?

Answer:

• No, protocol just contains method declarations.

protocol AProtocol {
		// You can delare property without assigning value
    var initialValue: Int { get set }
	  // You can make read-only property
		var getOnly: Int { get }
    // You can have function without defining its body
    func add()
		func subtract()
}

struct Calculator: AProtocol {

		var initialValue: Int
		var getOnly: Int

		func add() {

		}

    func subtract() {

    }


}

3) Can we extend Protocols?

Answer:

• Yes. To provide default implementations, we can extend protocols.

protocol AProtocol {
		// You can delare property without assigning value
    var initialValue: Int { get set }
	  // You can make read-only property
		var getOnly: Int { get }
    // You can have function without defining its body
    func add()
		func subtract()
}

// Through extension, you can define properties and methods
extension AProtocol {

    // You can assign values within extension
    var initialValue: Int {
        get {
            return 0
        }
        set {

        }
    }

		var getOnly: Int {
			get {
					return 0
			}
		}

    // You can make body within extension
    func add() {
        print("Add")
    }

}

struct Calculator: AProtocol {

    // You must implement subtract() method because it doesn't have body
    func subtract() {

    }


}

4) How to adopt protocols or how to conform protocol?

Answer:

extension ObjectName: ProtocolName {

}

5) How to declare ‘class-only’ adoptable protocol?

Answer:

• By making protocol extend AnyObject.

protocol AProtocol: AnyObject {
    var initialValue: Int { get set }
    func add()
}

// Compile Error
struct Calculator: AProtocol {

}

6) How to declare Optional Methods and Properties in Protocols?

Answer:

• Use
  • @objc optional var variableName: Int { get set }
  • @objc optional func methodName()
  • But this protocol is only available to class-type

7) What are the advantages of Protocols?

Answer:

• To achieve multiple inheritance
• To achieve delegation
• To segregate specific feature methods into a single unit

protocol AProtocol {
    var property1: String { get set }
    func method1()
}

protocol BProtocol {
    var property2: String { get set }
    func method2()
}

struct aStruct: AProtocol, BProtocol {
    var property1: String

    func method1() {

    }

    var property2: String

    func method2() {

    }

}

8) How to provide default implementation for protocol methods?

Answer:

• Yes, by using protocol extensions we can provide default behavior for the protocol methods.

protocol AProtocol {
		// You can delare property without assigning value
    var initialValue: Int { get set }
	  // You can make read-only property
		var getOnly: Int { get }
    // You can have function without defining its body
    func add()
		func subtract()
}

// Through extension, you can define properties and methods
extension AProtocol {

    // You can assign values within extension
    var initialValue: Int {
        get {
            return 0
        }
        set {

        }
    }

		var getOnly: Int {
			get {
					return 0
			}
		}

    // You can make body within extension
    func add() {
        print("Add")
    }

}

struct Calculator: AProtocol {

    // You must implement subtract() method because it doesn't have body
    func subtract() {

    }


}

9) Can we declare stored properties in Protocols?

Answer:

• No, Protocols do not contain stored properties. We must specify the declared property is get only or get and set.

protocol AProtocol {
		// You can delare property without assigning value
    var initialValue: Int { get set }
}

// Through extension, you can define properties and methods
extension AProtocol {

    // You can assign values within extension
    var initialValue: Int {
        get {
            return 0
        }
				set {

				}
    }


}

10) What is the default behavior of Protocol Methods?

Answer:

• By default, all methods in Protocol are required.

11) Can we declare an optional variable as let?

Answer:

• No, Optional variables are not expected to have a value in future. So to set or assign a value in future, the optional variable must be var.

12) Is Swift Object-Oriented Language or Protocol Oriented Programming Language?

Answer:

• Swift is Protocol Oriented Programming Language.

Table Of Contents

Section 1, Data Type

Section 2, Operator

Section 3, Conditional Statement

Section 4, Enum

Section 5, functions

Section 6, struct

Section 7, initializers

Section 8, closures

Section 9, OOP

Section 10, static type vs dynamic type

Section 11, optional

Section 12, generic

Section 13, subscript

Section 14, access specifier

Section 15, higher order function

Section 16, delegate

Section 17, extension

Section 18, Memory Management

Section 19, protocols

Section 20, collections

Section 21, KVO and KVC

Section 22, Exception Handling

Section 23, Framework

Section 24, Objective-C