iOS------[__NSDictionaryI remove

现象1

NSMutableDictionary*dict = [[NSMutableDictionary alloc]initWithDictionary:@{@"type":@"",@"START_NO":@"",@"END_NO":@"",@"SUM":@"",@"DOC_TYPE":@"",@"CCY":@"",@"FLAG":@""}];

NSArraylista =[[NSArray alloc]initWithObjects:dict, nil];
for (NSMutableDictionarydict in lista) {

    [dict removeObjectForKey:@"type"];
}
NSLog(@"%@",lista);

输出为：
(
{
CCY = "";
"DOC_TYPE" = "";
"END_NO" = "";
FLAG = "";
"START_NO" = "";
SUM = "";
}
)

现象2：
NSMutableDictionarydict = [[NSMutableDictionary alloc]initWithDictionary:@{@"type":@"",@"START_NO":@"",@"END_NO":@"",@"SUM":@"",@"DOC_TYPE":@"",@"CCY":@"",@"FLAG":@""}];
NSMutableArraylista =[[NSMutableArray alloc]init];
[lista addObject:dict];

for (NSMutableDictionary*dict in lista) {
    
    [dict removeObjectForKey:@"type"];
}
NSLog(@"%@",lista);

(
{
CCY = "";
"DOC_TYPE" = "";
"END_NO" = "";
FLAG = "";
"START_NO" = "";
SUM = "";
}
)

总结：
不管数组是可变或者是不可变的，只要数组内的字典为可变的，那就可以删除字典内的元素，以for in 顺便也将数组中字典的删除。

现象3：
NSDictionarydict = @{@"type":@"",@"START_NO":@"",@"END_NO":@"",@"SUM":@"",@"DOC_TYPE":@"",@"CCY":@"",@"FLAG":@""};
NSMutableArraylista =[[NSMutableArray alloc]init];
[lista addObject:dict];

for (NSMutableDictionary*dict in lista) {
    
    [dict removeObjectForKey:@"type"];
}
NSLog(@"%@",lista);

结果：*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSDictionaryI removeObjectForKey:]: unrecognized selector sent to instance 0x600003ad0d20'

总结：不管数组是可变还是不可变的，如果数组内的字典为不可变的，NSMutableDictionary*dict in lista的字典还是不可变的，切记。