过滤有什么区别：Dart 中的 Where 和 takeWhile

Question

I see both of them ( where and takeWhile ) has the same function.. or I might miss something here!

Answer 1

The documentation for Iterable.where says:

Returns a new lazy Iterable with all elements that satisfy the predicate test .

The documentation Iterable.takeWhile says:

Returns a lazy iterable of the leading elements satisfying test .

(emphasis added).

In other words, Iterable.takeWhile will stop iterating once it reaches the first item that does not satisfy the test callback.

A concrete example:

var list = [1, 1, 2, 3, 5, 8];
print(list.where((x) => x.isOdd).toList()); // Prints: [1, 1, 3, 5]
print(list.takeWhile((x) => x.isOdd).toList()); // Prints: [1, 1]