CODEWITHSUNDEEP
kotlin
Brice Harismendy
Brice Harismendy

Reputation: 113

How to specify particular setter for property of a class?

I'm following a course in kotlin and they speak about how to make a special setter but I don't know how to make it working here is my code :

class Course (val id:Int, title:String, var duree:Int, var state:Boolean){
var title:String = title
    get(){return field}
    set(value){field = "my awesome" + value}
 }
 
 fun main(args: Array<String>) {
    var myCourse:Course = Course (0, "stuff", 50, true)
    println(myCourse.title)
 }

but it keep output 'stuff' instead of 'my awesome stuff'

Upvotes: 1

Views: 61

Answers (3)

Madhu Bhat
Madhu Bhat

Reputation: 15183

var myCourse:Course = Course(0, "stuff", 50, true)

With the above line of code, the Course object is initialized with the constructor. Here the setter is not called, hence it prints stuff and not my awesome stuff. The setter would get called only if you use

myCourse.title = "stuff"

If you want the setter to be called on initialization, you need to set the value of title in an init block as below

class Course(val id: Int, title: String, var duree: Int, var state: Boolean) {

    var title: String = title
        set(value) {
            field = "my awesome $value"
        }

    init {
        this.title = title
    }
}

Or, you can drop the custom setter and set the value of title with your custom value in the init block itself

class Course(val id: Int, var title: String, var duree: Int, var state: Boolean) {

    init {
        this.title = "my awesome ${this.title}"
    }
}

Upvotes: 4

Pietro Martinelli
Pietro Martinelli

Reputation: 1906

I was able to get you example working applying a little change in your code:

class Course (val id:Int, __title:String, var duree:Int, var state:Boolean){
    var title:String = ""
        get() { return field}
        set(value){field = "my awesome" + value}
        
    init {
        title = __title
    }
 }

The difference seems to be the explicit assignment title = __title, that forces the usage of the custom setter...

Upvotes: 1

Tenfour04
Tenfour04

Reputation: 93609

The custom setter is only used when you explicitly set the value. The custom setter is not used when you initialize the backing field at the declaration site using = title.

If you want the custom setter to be applied using the initial value, you can add an init block to your class:

    init {
        this.title = title
    }

Upvotes: 1

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