Skip to main content

Execute a method when a variable value changes in Swift

This post is about how to execute a function when a variable value changes.

Instead of key-value observation, simply use a property observer for the variable. 

For e.g:

Whenever the value of variable named allSlot changes, the two lines will execute which are written in the didSet method.
private var allSlot: [String] = [] {
        didSet {
            slotTableView?.reloadData()
            enableRightBarButton()
        }
    }

Comments

Popular posts from this blog

Vector graphics in iOS

In past, designers had to create multiple versions of the same asset (1x, 2x, 3x) to satisfy multiple screen sizes. Using vector assets can save you time because you only have to generate the asset once.  You just need an .xcassets  file in your project for storing your images. In there, you can declare image sets to be “Vectors”. A vector file contains a lot of metadata of an asset that tells the system how to render it's contents, independent of the screen's resolution.  This also means that whenever we get larger screen resolutions, Xcode will be able to scale up your images from your already existing vector PDF for you, giving you automatic support for future devices for free. Steps:- Select “New Image Set” in your  XCAsset. Select the Attributes Inspector in Utilities panel. Under the types drop-down menu, select "Vector" Drag and drop your vector PDF Use the Xcode image catalog image set as you would with any other image. For instance, calling --im

Disabling print for Production In Swift Project

You'll need to set up a compiler flag to use the Swift preprocessor - go to the Swift Compiler - Custom Flags section of Build Settings to set up a -D DEBUG flag: Then in your code you can define a DLog() function and only print your message if the DEBUG flag is set: func DLog (message: String , function: String = __FUNCTION__) {     #if DEBUG     println( "\(function): \(message)" )     #endif }

Return multiple values from a function in objective C

We can return tuples in swift as follows:- func getData () -> ( Int , Int , Int ) { //...code here return ( hour , minute , second ) } You can't do that in objective-c. Best option is using parameters by reference . Something like this. - ( void ) getHour :( int *) hour minute :( int *) minute second :( int *) second { * hour = 1 ; * minute = 2 ; * second = 3 ; } And use it like this. int a , b , c ; [ self getHour :& a minute :& b second :& c ]; NSLog (@ "%i, %i, %i" , a , b , c );