xcode 如何通过键删除 NSMutableArray 对象？
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how to remove an NSMutableArray object by key?
提问by Mahmoud
i have structured an NSMutableArray and here is an example
我已经构建了一个 NSMutableArray，这是一个例子
( { Account = A; Type = Electricity; }, { Account = B; Type = Water; }, { Account = C; Type = Mobile; } )
( { Account = A; Type = Electricity; }, { Account = B; Type = Water; }, { Account = C; Type = Mobile; } )
when i try to delete Account B using
当我尝试使用删除帐户 B 时
[data removeObject:@"B"];
[数据删除对象：@"B"];
Nothing Happens
没发生什么事
[[NSUserDefaults standardUserDefaults] synchronize];
NSArray *archivedArray = [NSKeyedUnarchiver unarchiveObjectWithFile:[self dataFilePath]];
if (archivedArray == nil) {
data = [[NSMutableArray alloc] init];
} else {
data = [[NSMutableArray alloc] initWithArray:archivedArray];
}
回答by jtbandes
If you're actually using an array and not a dictionary, you need to search for the item before you can remove it:
如果您实际上使用的是数组而不是字典，则需要先搜索该项目，然后才能删除它：
NSUInteger index = [data indexOfObjectPassingTest:^BOOL (id obj, NSUInteger idx, BOOL *stop) {
return [[(NSDictionary *)obj objectForKey:@"Account"] isEqualToString:@"B"];
}];
if (index != NSNotFound) {
[data removeObjectAtIndex:index];
}
回答by Dair
Alternative: try a NSMutableDictionary:
替代方案：尝试一个NSMutableDictionary：
NSArray *accounts = [NSArray arrayWithObjects:@"A", @"B", @"C", nil];
NSArray *types = [NSArray arrayWithObjects:@"Electricity", @"Water", @"Mobile", nil];
NSMutableDictionary* data = [NSMutableDictionary dictionaryWithObjects:types forKeys:accounts];
[data removeObjectForKey:@"B"];
回答by Antwan van Houdt
An NSArrayis like a list of pointers, each pointer points to an object.
AnNSArray就像一个指针列表，每个指针都指向一个对象。
If you call:
如果你打电话：
[someArray removeObject:@"B"];
You create a new NSStringobject that contains the string "B". The address to this object is different from the NSStringobject in the array. Therefore NSArraycannot find it.
您创建一个NSString包含字符串“B”的新对象。此对象的地址NSString与数组中的对象不同。因此NSArray找不到它。
You will need to loop through the array and determine where the object is located, then you simply remove it by using removeObjectAtIndex:
您将需要遍历数组并确定对象所在的位置，然后您只需使用 removeObjectAtIndex:
