Null aware function invocation operator

Question

In the same way we can have

nullableClassInstance?.method(blah)

Is there a way to do

nullableFunctionInstance?(blah)

In other words, is there an operator that checks whether a function instance is not null, if so, invoke the function all in one line?

see https://stackoverflow.com/a/61141239/6665568 – Natesh bhat May 08 '20 at 12:03 — Natesh bhat, May 08 '20 at 12:03

score 181 · Accepted Answer · edited Mar 19 '20 at 05:48

181

Using the call method, you can achieve what you want with:

nullableFunctionInstance?.call(blah)

There's also the apply method if you want to pass arguments.

edited Mar 19 '20 at 05:48

Philippe Fanaro

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answered Jul 10 '17 at 22:09

Ganymede

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But I have to wrap my function in a callable class or am I misunderstanding this? Invoking "call" or "apply" on a variable of type e.g. 'void Function(int)' throws a compiler error – Wecherowski Jan 25 '20 at 22:43

score 18 · Answer 2 · answered Apr 10 '20 at 13:24

If you have a Function Object , you can use the call method and send all the parameters to that which works exactly as calling the function. Here , you can use the null aware member access operator.

void myFun(int a , int b){...}

var myVar = myFun ;

call

The function myVar will only get called if its not null as shown below.

myVar?.call( arg1 , arg2 );

apply

If your function is dynamic or you wish to control which function is being called at run time , you can use the apply static method of Function like so :

Function.apply(myVar , [arg1 , arg2]);

apply takes the function and a List of parameters that will be sent to the function.

Null aware function invocation operator

2 Answers2

call

apply

Linked

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