| Function | Argument/Receiver | Lambda Result | Remark |
|---|---|---|---|
| let | it | yes | |
| also | it | no/self | |
| run | this | yes | |
| apply | this | no/self | |
| with | this | yes | not extension |
Discussion on run vs with
- https://discuss.kotlinlang.org/t/let-vs-with-vs-run/30
- https://stackoverflow.com/questions/38501764/difference-between-with-and-run-in-kotlin
- https://discuss.kotlinlang.org/t/spreadsheet-for-differences-between-let-with-run-apply-and-also/5029
let
- provide argument
it - return a result (can be Any)
val name: String? = "hello"val result = name?.let { it.toUpperCase()}assertEquals(result, "HELLO")val result = name?.let { it.toUpperCase() 100}assertEquals(result, 100)val result = name?.let {}assertEquals(result, Unit)also
- provide argument
it - doesn't return a result / same object
val name: String? = "hello"val result = name?.also { it.toUpperCase()}assertEquals(result, "hello")val result = name?.also { it.toUpperCase() 100}assertEquals(result, "hello")val result = name?.also {}assertEquals(result, "hello")run
- change argument
this - return a result (can be Any)
val name: String? = "hello"val result = name?.run { toUpperCase()}assertEquals(result, "HELLO")val result = name?.run { toUpperCase() 100}assertEquals(result, 100)val result = name?.run {}assertEquals(result, Unit)apply
- change argument
this - doesn't return a result / same object
val name: String? = "hello"val result = name?.apply { toUpperCase()}assertEquals(result, "hello")val result = name?.apply { toUpperCase() 100}assertEquals(result, "hello")val result = name?.apply {}assertEquals(result, "hello")with
- change argument
this - return a result (can be Any)
- not extension function
- not suited for null checking or call chaining
val result = with(name) { this?.toUpperCase()}assertEquals(result, "HELLO")val result = with(name) { this?.toUpperCase() 100}assertEquals(result, 100)val result = with(name) {}assertEquals(result, Unit)