Kotlin Inline Functions With Example

Kotlin Inline Functions request compiler to copy parameters and functions to the calling place and not allocate memory. So basically inline functions are used to reduce memory.

Kotlin Inline Functions are declared by using keyword inline. In inline functions, we can pass lambda functions to reduce memory.

 

fun main(args: Array<string>) {
     playerName({ println(“Cristiano”)})
}

inline fun playerName(myCall: () -> Unit ) {
     myCall()
     print(“Ronaldo”)
}

 

When we want some lambda function to not be inclined in inline functions, then we use noinline modifier to mark that function.

 

fun main(args: Array<string>) {
     playerName({println(“Cristiano”)}, {println(“Lional”)})
}

inline fun playerName(myCall1: () -> Unit, noinline myCall2: () -> Unit) {
     myCall1()
     myCall2()
     println(“Neymar”)
}

 

Cristiano
Lional  
Neymar

 

A normal return statement is not allowed in lambda functions. If we want explicitly return from lambda, We have to use label. Because a lambda can not make enclosing function return but if the lambda function is passed in inline function then return is allowed.

 

fun main(args: Array<string>) {
     playerName({println(“Cristiano”) return}, {println(“Lional”)})
}

inline fun playerName(myCall1: () -> Unit, noinline myCall2: () -> Unit) {
     myCall1()
     myCall2()
     println(“Neymar”)
}

 

Cristiano

 

crossinline modifier is used to prevent return in lambda expression. If return is found in lambda expression then crossinline modifier will throw compile time error.

 

fun main(args: Array<string>) {
     playerName({println(“Cristiano”) return //compile time error}, {println(“Lional”)})
}

inline fun playerName(crossline myCall1: () -> Unit, noinline myCall2: () -> Unit) {
     myCall1()
     myCall2()
     println(“Neymar”)
}

 

If we want to access type of parameter passed during the call then we need to use reified modifier.

 

fun main(args: Array<string>) {
     playerName<string>()
}

inline fun playerName() {
     print(T::class)
}

 

class kotlin.String

 

We can also inline properties and inline just specific accessor of property in kotlin programming language using inline modifier.

 

fun main(args: Array<string>) {
     print(flag)
}
fun jerseyNo(i: Int): Int{
     var j = i
     return j
}
inline var flag : Boolean
     get() = jerseyNo(7) == 7
     set(flag) {flag}

 

fun main(args: Array<string>) {
     print(flag)
}
fun jerseyNo(i: Int): Int{
     var j = i
     return j
}
var flag : Boolean
inline get() = jerseyNo(7) == 7
set(flag) {flag}