CODEWITHSUNDEEP
functionclasskotlin
Malcolm
Malcolm

Reputation: 41

How to pass data in a data class to a function

I need to use a function to print data from a data class and having read some other answers on this site, but I am still unclear on how to do it. Help would be appreciated!

data class Chemical(
    val key: String,
    val name : String,
    val formula : String
)

fun printans(Chemical(q):: data class) {

    println("Key = $q.key,  Name = $q.name Formula = $q.formula")

}

fun main(args: Array<String>) {

    val cuso4 = Chemical("001", "Copper(II) sulphate", "CuSO4")
    val cacl2 = Chemical("002", "Calcium chloride", "CaCl2")

    printans(cuso4)
    printans(cacl2)
}

I have dozens of errors reported eg:

test.kt:9:22: error: expecting comma or ')'
fun printans(Chemical(q):: data class) {

test.kt:11:2: error: expecting member declaration
    println("Key = $q.key,  Name = $q.name Formula = $q.formula")

etc

Upvotes: 0

Views: 243

Answers (3)

Nizan Ifrach
Nizan Ifrach

Reputation: 141

You can use Kotlin extended function feature! Like so:

fun Chemical.printans(){
println("Key = ${this.key},  Name = ${this.name} Formula = ${this.formula}")
}

And just invoke it:

val chemical = Chemical("Key", "Name", "Formula")
chemical.printans()

You can read more on extended functions here

Upvotes: 0

Willi Mentzel
Willi Mentzel

Reputation: 29844

Your syntax is wrong and since Chemical is a data class, you don't even need to build the string yourself, it will already be built for you:

fun printans(c: Chemical) {
    println(it)
}

Chemical(key=foo, name=bar, formula=baz)

So, you could even simplify to println(c), and not use a dedicated function since it does not do anything more than println would do.

If this format is not what you want, I would recommend to override toString of Chemical.

data class Chemical(/* ... */) {
    fun toString(c: Chemical) = "Key = ${c.key},  Name = ${c.name} Formula = ${c.formula}"
}

This way, no matter where you pass it to println, the output will always be in your desired format, because println calls toString under the hood.

Upvotes: 1

Andrew Churilo
Andrew Churilo

Reputation: 2309

Add braces and use q: Chemical instead Chemical(q):: data class.

fun printans(q: Chemical) {
    println("Key = ${q.key},  Name = ${q.name} Formula = ${q.formula}")
}

Upvotes: 0

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