Question

我有一个NSMutableArray作为视图控制器类中的属性，并且该行正在另外两个类中使用。其中一个类操作数组（向它添加更多对象），另一个类只读取它。当其中一个类操作数组时，它在视图控制器类中没有被修改，它被实例化。因此，第三个类没有得到它需要的正确日期。

在视图控制器类中：

@property (nonatomic, strong) NSMutableArray *entityLines;

在其他两个班级中：

@property (nonatomic, weak) NSMutableArray *linesToDraw;
@property (nonatomic, weak) NSMutableArray *linesForKey;

数组初始化：

- (id)init
{
    self = [super init];
    if (self) {
        self.title = @"Line graph";
        lineQuery = [[LineGraphQuery alloc] init];
        entityLines = [NSMutableArray array];
    }

    return self;
}

修改数组：

     - (void)drawRect:(CGRect)rect
{
    if(data.namedEntityData.count > 0) {
        CGContextRef context = UIGraphicsGetCurrentContext();
        CGContextSetLineWidth(context, LINE_WIDTH);
        CGContextSetLineCap(context, kCGLineCapRound);
        CGContextSetFillColorWithColor(context, [[UIColor blackColor] CGColor]);
        CGContextFillRect(context, rect);

        [self clearAllLines];
        for(NSString *key in [data.namedEntityData allKeys]) {
            EntityLine *entityLine = [self getNamedEntityLineForName:key];
            if(!entityLine) {
                entityLine = [[EntityLine alloc] init];
                entityLine.name = key;
                entityLine.color = [self getRandomColor];
            }
            float intervalX = STARTING_INTERVAL_X;
            float lastRangeY = MIN_EVENT_COUNT_Y;

            CGContextSetStrokeColorWithColor(context, [entityLine.color CGColor]);
            NSArray *events = [data.namedEntityData objectForKey:key];
            NSInteger rangeDifference = data.endYear - data.beginYear;

            for(int i = 0; i < numberOfDateRangeIntervals; i++) {
                int startYearRange = data.beginYear + (i * (rangeDifference / numberOfDateRangeIntervals));
                int endYearRange = (i == numberOfDateRangeIntervals - 1) ? data.endYear : data.beginYear + ((i + 1) * (rangeDifference / numberOfDateRangeIntervals) - 1);
                int eventCount = [self getCountForEvents:events withBeginYear:startYearRange andEndYear:endYearRange];

                Line *line = [[Line alloc] init];
                line.begin = CGPointMake(intervalX, lastRangeY);
                CGContextMoveToPoint(context, line.begin.x, line.begin.y);
                intervalX += intervalXIncrement;
                lastRangeY = [self getYCoordinateForEventCount:eventCount];
                line.end = CGPointMake(intervalX, lastRangeY);
                [entityLine addLine:line];

                CGContextAddLineToPoint(context, line.end.x, line.end.y);
                CGContextStrokePath(context);
            }
            [linesToDraw addObject:entityLine];
        }

        [self drawEventCountLabelsWithContext:context];
        [self drawDateRangeLabelsWithContext:context];
    }
}

- (void)clearAllLines
{
    for(EntityLine *line in linesToDraw)
        [line clearLines];
}

其他类设置对NSMutableArray的引用：

lineGraph.linesToDraw = self.entityLines;
lineKey.linesForKey = self.entityLines;

Answer 1

在不同的类中赋予属性（或实例变量）相同的名称不会导致它们指向相同的对象。创建数组后，需要将指向数组的指针传递给其他类实例中的属性。

@interface ABCFirstClass ()

@property (nonatomic, strong) NSMutableArray *lines;
@property (nonatomic, strong) ABCAnotherClass *otherClass;  // Also has a property named "lines".

@end


@implementation ABCFirstClass

- (id)init
{
    self = [super init];
    if (self) {
        self.lines = [NSMutableArray arrayWithObjects:@"1", @"2", @"3", nil];
        self.otherClass = [[ABCAnotherClass alloc] init];
        self.otherClass.lines = self.lines;
          // Now both classes have a pointer to the same array object.
    }
    return self;
}

这不需要在-init方法中发生。也许一个完全不同的类从一个获取指针并将其传递给另一个。

请注意，我通常直接在-init（_lines，_otherClass）中使用ivars，但我想保持这个示例简单。

在其他类中操作时，NSMutableArray未被正确修改

1 个答案: