ios - How to check if a UILabel is empty and append content to a label? -

new ios , swift. want best practice tips. want append content label in new line. try:

@iboutlet weak var history: uilabel! @ibaction func appendcontent() {     if history.text != nil  && !history.text!.isempty  {         history.text = history.text!  + "\r\n" + "some content"     }     else{         history.text = digit     } } 

it seems work, however,

1. is there better way check text not nil , not empty?
2. is there "keyword" thing "\r\n"?

you can use optional binding: if let check if nil.

example 1:

if let text = history.text !text.isempty {     history.text! += "\ncontent" } else {     history.text = digit } 

or can use map check optionals:

example 2:

history.text = history.text.map { !$0.isempty ? $0 + "\ncontent" : digit } ?? digit 

!$0.isempty in cases not needed code can bit better:

history.text = history.text.map { $0 + "\ncontent" } ?? digit 

edit: what map do:

the map method solves problem of transforming elements of array using function.

let’s have array of ints representing sums of money , want create new array of strings contains money value followed “€” character i.e. [10,20,45,32] -> ["10€","20€","45€","32€"].

the ugly way of doing creating new empty array, iterating our original array transforming each element , adding new array

var stringsarray = [string]()  money in moneyarray {     stringsarray += "\(money)€" } 

using map just:

let stringsarray = moneyarray.map { "\($0)€" } 

it can used optionals:

the existing map allows apply function value inside optional, if optional non-nil. example, suppose have optional integer , want double it. write i.map { $0 * 2 }. if has value, optional of value doubled. on other hand, if nil, no doubling takes place.

(source)

what ?? do:

the nil coalescing operator (a ?? b) unwraps optional if contains value, or returns default value b if nil. expression of optional type. expression b must match type stored inside a.

the nil coalescing operator shorthand code below:

a != nil ? a! : b