What does 'yield' keyword do in flutter?

Question

What does the yield keyword actually do in Dart?

Answer 1

The yield statement can be used only in generator's functions.
The generator's function generates data items in natural way (as calculated, received from outside, predefined values etc).
When next data item is ready then the yield statement send this item into data sequence which is essentially the generation result of the function.
The data sequence can be synchronous or asyncronous.
In Dart language the synchronous data sequence means the instance of Iterable.
The asynchronous data sequence means the instance of Stream.

P.S.
Generator functions can generate data items indefinitely until the function returns.
But unlike normal functions, the result (the data sequence) will be returned immediately after the function call and can be used immediately.
The end of the data sequence, in this case, can be reached only when generator function will be terminated (successfully or by failure).