iOS:在for循环(双条目)中，在NSArray中插入NSDictionary时的奇怪行为

Question

当应用程序处于for循环中时，我试图将NSMutableDictionary插入到NSMutabbleArrey中时，遇到了一个非常奇怪的行为。

NSMutableDict是在每个for步骤中构造的，并添加到数组中。但它不起作用。。。当我在for循环后打印出数组时，数组中的每个NSMutableDictionary都是相同的-经过一些日志记录，我看到每个for步骤，数组中所有的dictionary都会被替换，并在末尾添加一个。。。这是一种奇怪的行为，我不知道是什么原因造成的。。。如果我将currentID（参见代码）添加到dictionary的数组中，那么最终，一切看起来都很好。。。这里有什么问题？

NSArray *relativeIAbnormality = [[NSArray alloc] init];
NSMutableDictionary *tempDict = [[NSMutableDictionary alloc] init];
NSMutableArray *tempArray = [[NSMutableArray alloc] init];
for (int q = 0; q < [measureData.list count]; q++) {
    [tempDict removeAllObjects];
    NSString *currentId = [[measureData.list objectAtIndex:q] valueForKey:@"id"];
    NSPredicate *predicate = [NSPredicate predicateWithFormat:@"id == %@", currentId];
    NSInteger count = [[lastMeasureData.list filteredArrayUsingPredicate:predicate] count];
    if(count > 0){
        // get the answer Value for the CURRENT measure
        float theValue = 0;
        theValue = [[[[measureData.list objectAtIndex:q] objectForKey:@"propertys"] valueForKey:@"answerValue"] floatValue];
        theValue = theValue/100;
        if(theValue > 10){
            theValue = 10;
        }else if (theValue < 0) {
            theValue = 0;
        }
        // get the answer Value for the LAST measure
        float theNewValue = 0;
        theNewValue = [[[[[lastMeasureData.list filteredArrayUsingPredicate:predicate] objectAtIndex:0] objectForKey:@"propertys"] valueForKey:@"answerValue"] floatValue];
        theNewValue = theNewValue/100;
        if(theNewValue > 10){
            theNewValue = 10;
        }else if (theNewValue < 0) {
            theNewValue = 0;
        }
        // gets the reltaive
        theValue = theValue - theNewValue;
        NSNumber *dif = [NSNumber numberWithFloat:theValue];
        [tempDict setObject:currentId forKey:@"id"];
        [tempDict setObject:dif forKey:@"dif"];
        //NSLog(@"tempDict: %@", tempDict);
        [tempArray addObject:tempDict];
        //NSLog(@"tempArray: %@", tempArray);
    }
}
//NSLog(@"full tempArray: %@", tempArray);

Answer 1

您一直在使用相同的tempDict实例。在循环中移动临时dict的alloc-init对。

NSArray *relativeIAbnormality = [[NSArray alloc] init];
NSMutableArray *tempArray = [[NSMutableArray alloc] init];
for (int q = 0; q < [measureData.list count]; q++) 
{
    NSMutableDictionary *tempDict = [[NSMutableDictionary alloc] init];
    ...
}