Is it possible to link javabean set methods?

1

For  javabean , we usually have to write this: Bean obj = new Bean() obj.setA(...) obj.setB(...) obj.setC(...) ...

Maybe it would be more convenient this way:

obj~.setA()~.setB()~.setC() .

outersky

2

You may write something like this: 

class A(val a : String = "", val b : Int = 0) {
}



…


A(a = “zzz”, b = 3)


Also note there are no methods setA and setB for class A

In some cases you can impelment with closure like this:

class A {
    var x : Int = 0



  fun with(closure : A.() -> Unit) : Unit {

  closure()

  }


}


…


a().with { x = 1 }


But don’t play with it too much… this approach have visibility problems

3

What if I have to use old java libraries ? There are pure javabeans everywhere.

Since in kotlin now we can do  list.filter(…).map(…).makeString(…) ,
I think it’s reasonable to make it more simple for using old javabeans.

thanks.

outersky

4

One option is to say something like 

with (obj) {
  setA()
  setB()
  setC()
}

Where with() is defined as follows:

fun <T> with(t : T, f : T.() -> Unit) {
  t.(f)()
}

Another would be to have an extension function for your obj:

fun MyPojo.set(a : A? = null, b : B? = null, c : C? = null) {
  if (a != null) setA(a)
  if (b != null) setB(b)
  if (c != null) setC(c)
}



// Usage


obj.set(a = aa, c = cc)

5

wow , it works.

Now it’s the same as in javascript :smiley:

but I’m a little confused, for:

fun <T> with(t : T, f : T.() -> Unit) {
  t.(f)()
}

Shouldn’t the second parameter “f” mean ONE member function of Object “t” ?
While

{

setA()

setB()

setC()

}
means a group of functions .

6 
with (obj) {
  setA();
  foo(1);
}

I’ve never made up my mind on whether this is a nice feature to have, any opinion on that? James?

Finally, two quick questions for Andrey:

What is the . for in:

f : T.() -> Unit

?

Also, your with definition only seems to allow for one statement, not multiple. Shouldn’t it be a varargs of closures?

7

It doesn't mean a group of functions. It means "a function literal", you can think of it as a block of code, but in this block, this has type T

8

What is the . for in: 

f : T.() -> Unit

?

Also, your with definition only seems to allow for one statement, not multiple. Shouldn't it be a varargs of closures?

Please have a look at extension function literals.

9

It does NOT work in M3. dropped or just a bug?

10

It's not exactly droppped, but we don't do it currently, because it causes problems with inheritance.