如何實現Iterable <E>

Question

我想將下面的Java代碼移植到Dart，並且對此感到困惑。

在Java中，Iterable接口是使用一種方法清理並實現此功能的地方。

此代碼如何最好地轉換爲Dart？

/** 
* Chess squares represented as a bitmap. 
*/ 
public class ChessSquares implements Iterable<ChessSquare> { 

private static class ChessSquaresIterator implements Iterator<ChessSquare> { 
    long bits; 
    int nextBit; 

    public ChessSquaresIterator(long bits) { 
     this.bits = bits; 
     nextBit = Long.numberOfTrailingZeros(bits); 
    } 

    @Override 
    public boolean hasNext() { 
     return (nextBit < 64); 
    } 

    @Override 
    public ChessSquare next() { 
     ChessSquare sq = ChessSquare.values()[nextBit]; 
     bits = bits & ~sq.bit; 
     nextBit = Long.numberOfTrailingZeros(bits); 
     return sq; 
    } 

    @Override 
    public void remove() { 
     throw new UnsupportedOperationException(); 
    } 
} 


@Override 
public Iterator<ChessSquare> iterator() { 
    return new ChessSquaresIterator(bits); 
} 

... 

Answer 1

Soo我嘗試過這種方法，因爲我不想擴展基類，所以這不是我想要的。

/** 
* Chess squares represented as a bitmap. 
*/ 
class ChessSquares extends IterableBase<ChessSquare> { 

    Iterator<ChessSquare> get iterator { 
    return new ChessSquaresIterator(this); 
    } 

    ... 

} 

class ChessSquaresIterator extends Iterator<ChessSquare> { 
    int _nextBit; 
    int64 _bits; 
    ChessSquare _current; 

    ChessSquaresIterator(ChessSquares squares) { 
    _bits = new int64.fromInt(squares._bits); 
    } 

    bool moveNext() { 
    _nextBit = _bits.numberOfTrailingZeros(); 
    if (_nextBit < 64) { 
     _current = ChessSquare.values()[_nextBit]; 
     _bits = _bits & ~_current.bit(); 
    } else { 
     _current = null; 
    } 
    return _nextBit < 64; 
    } 

    E get current => _current; 
} 

Answer 2

使用IterableMixin你只需要實現iterator -function。

class ChessSquares extends Object with IterableMixin<ChessSquare> { 
    Iterator<ChessSquare> iterator() => new ChessSquaresIterator(bits); 
    ... 
} 

對混入一個簡短的介紹訪問http://blog.sethladd.com/2013/03/first-look-at-dart-mixins.html。

Iterator-界面很簡單。您只需執行功能moveNext和獲取者current。