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Variables and Constants in Swift.

neeraj3508 profile image Neeraj Gupta ・2 min read

Brief Introduction About Swift

Swift is a language developed by Apple which is made using modern approach, include safety features and software design patterns. As the name suggests swift is fast, safe and easy to use. It is basically made a replacement for c-based family(C, C++ and Objective-C). It can be used to make apps and can be also used for cloud services and it is among the fastest growing languages.

What are Variables and Constants?

As the name suggests, values that can be varied later according to needs.

Variables and Constants are like containers for storing values. Let's say i have a box in which i stored a number 10, but later on i wished to change it to let's say 6 then what i will do is take the old value out and put a new value inside that box.

But not the same happens in case of Constants. As their name suggests, their value remain constant over time and cannot be changed. Here if is stored 10 then it's gonna remain 10 and cannot be changed.

How To Declare Variables and Constants ?

Comments in Swift : We use // for comments in swift.Comments are like if we do not want to include something in our code but we want it to be present in our code snippet. So compiler while compiling will ignore these comments.

Variables
They are defined with keyword var.

var variableOne = 10 // assigned value of 10 to a variable
// Swift has a cool feature of type inference that means that swift will automatically decides the type of variable for you. Like in above line swift will say okay this is variable of type Integer
var stringOne = "Hello, World!"
// Here swift will automatically infer the type of variable as String
var doubleOne = 1.00
//Here Swift will infer this variable as of type Double
var boolOne = true
//Here Swift will infer the type of variable as type Bool
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var x = 1
x = 2
print(x) // this will print value of x as 2 
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Constants
They are defined using keyword let

let x = 1
x = 2 // Swift will give error here as x is declared as constant in above line
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Type Annotation - In above part we saw that Swift has power to infer the type of variable but what if we want to play safe and declare type of variable ourselves.

var a : Int // Here we are saying that we have variable a of type Int
var b : Double // Here we are saying that we have variable b of type Double

var c : String // Here we are saying that we have variable c of type String

var d : Bool // Here we are saying that we have variable d of type Bool
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Note : Semicolons after end of every statement are optional in Swift.

This was all about Variables and Constants in Swift. I haven't included data types in detail but we will see that in next post.

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