Question

我一直在尝试使用NSPredicate来过滤这个数组（它充满了NSDictionaries）...

我的代码数量很少，但是没有用......

以下代码应将label.text更改为AmyBurnett34，但它不会......

NSPredicate *pred = [NSPredicate predicateWithFormat:@"id = %@", [[mightyPlistDict objectForKey:@"pushesArr"] objectAtIndex:indexPath.row]];

    NSLog(@"%@",pred);

    label.text = [[[twitterInfo filteredArrayUsingPredicate:pred] lastObject] objectForKey:@"screen_name"];
    NSLog(@"%@",twitterInfo);

以下是NSLoged的内容......

2012-08-05 11:39:45.929 VideoPush[1711:707] id == "101323790"
2012-08-05 11:39:45.931 VideoPush[1711:707] (
        {
        id = 101323790;
        "screen_name" = AmyBurnett34;
    },
        {
        id = 25073877;
        "screen_name" = realDonaldTrump;
    },
        {
        id = 159462573;
        "screen_name" = ecomagination;
    },
        {
        id = 285234969;
        "screen_name" = "UCB_Properties";
    },
        {
        id = 14315150;
        "screen_name" = MichaelHyatt;
    }
)

如果您还要NSLog这个......那么阵列是空的......

NSLog(%@,[twitterInfo filteredArrayUsingPredicate:pred]);

Answer 1

问题是您的谓词正在使用字符串进行比较，而您的内容正在使用数字。试试这个：

NSNumber *idNumber = [NSNumber numberWithLongLong:[[[mightyPlistDict objectForKey:@"pushesArr"] objectAtIndex:indexPath.row] longLongValue]];
NSPredicate *pred = [NSPredicate predicateWithFormat:@"id = %@", idNumber];

Answer 2

您不确定“id”的值是否为字符串 - 它可能是NSNumber。我建议：

NSUInteger matchIdx = ...;
NSUInteger idx = [array indexOfObjectPassingTest:^BOOL(NSDictionary *dict, NSUInteger idx, BOOL *stop)
{
  id obj = [dict objectForKey:@"id"];
  // NSLog the class if curious using NSStringFromClass[obj class];
  NSUInteger testIdx = [obj integerValue]; // works on strings and numbers
  return testIdx == matchIdx;
}
if(idx == NSNotFound) // handle error

NSString *screenName = [[array objectAtIndex:idx] objectForKey:@"screen_name"];

Answer 3

NSPredicate用于过滤数组，而非排序数组。要对数组进行排序，请使用NSArray的sortedArrayUsingDescriptors方法。

一个例子：

// Define a sort descriptor based on last name.
NSSortDescriptor *descriptor = [[NSSortDescriptor alloc] initWithKey:@"lastName" ascending:YES];    

// Sort our array with the descriptor.
NSArray *sortedArray = [originalArray sortedArrayUsingDescriptors:[NSArray arrayWithObjects:descriptor, nil]];

使用NSPredicate过滤NSArray / NSDictionary

3 个答案: