iOS App Development: Swift basics

let -> make a constant

var -> make a variable

In order to assign a value, we may not write type explicitly

Example:

     let constantValue = 20

        let constantValue2 : Int = 20

 Error:  Cannot assign to 'let' value 'constantValue'

  constantValue = 30.5

 Error:  Cannot assign to 'let' value 'constantValue2’

        constantValue2 = 30

Change let to var

   var Value = 20

        var Value2 : Int = 20

Error: Type 'Int' does not conform to protocol 'FloatLiteralConvertible'

        Value = 30.5

  It’s OK

        Value2 = 30

Convert to “Int” type to “String” type

  let stringValue = "The height of frame is "

        let height = 100

        let ​heightLabel​ = stringValue + String(height)

        println(​heightLabel​)

Convert to any type to String type basically.

     let height = 100

        let stringValue = "The height of frame is  \(height)"

        let ​heightLabel​ = stringValue

        println(​heightLabel​)

Change an item of array

        var arrayList = ["cat","dog","bird"]

        arrayList[1] = "penguen"

        for var i=0; i<arrayList.count; i++

        {println(arrayList[i])

}

Add an item of array by using append method

        arrayList.append("bear")

Add an array of one or more compatible items

        arrayList += ["cow","butterfly"]

To insert an item into the array at a specified index:

        arrayList.insert("bee", atIndex: 4)

To remove an item from array

   arrayList.removeAtIndex(5)

iOS App Development