試圖過濾NSMutableArray與NSPredicate並獲取錯誤

Question

我想過濾員工聯繫人列表的結果，我留在我的應用程序，但我得到以下錯誤：'不能用於/包含操作符與集合最後（不是一個集合）'

我已經嘗試了NSPredicate命令，self，self.last，employee.last，last =='smith'（這個不會產生錯誤，但不會產生錯誤， t返回任何結果）。

NSMutableArray *employeesList = [[NSMutableArray alloc] init]; 
Person2 *employee = [[Person2 alloc] init]; 

employee.first = @"bob"; 
employee.last = @"black"; 
[employeesList addObject:employee]; 

employee = [[Person2 alloc] init]; 
employee.first = @"jack"; 
employee.last = @"brown"; 
[employeesList addObject:employee]; 

employee = [[Person2 alloc] init]; 
employee.first = @"george"; 
employee.last = @"smith"; 
[employeesList addObject:employee]; 

NSPredicate *predicate = [NSPredicate predicateWithFormat:@"last contains[cd] %@", @"black"]; 
NSArray *filteredKeys = [employeesList filteredArrayUsingPredicate:predicate]; 
NSLog(@"filtered : %@",filteredKeys); 

[person2.h]

@interface Person2 : NSObject 

{ 
    @private 
} 

@property (nonatomic, retain) NSString *first; 
@property (nonatomic, retain) NSString *last; 

+ (Person2 *)personWithFirst:(NSString *)first andLast:(NSString *)last; 

@end 

[person2.m]

#import "Person2.h" 

@implementation Person2 
@synthesize first, last; 

- (id)init { 
    self = [super init]; 
    if (self) { 
    } 

return self; 
} 

+ (Person2 *)personWithFirst:(NSString *)first andLast:(NSString *)last { 
Person2 *person = [[Person2 alloc] init]; 
[person setFirst:first]; 
[person setLast:last]; 
return person; 
} 

- (NSString *)description { 
return [NSString stringWithFormat:@"%@ %@", [self first], [self last]]; 
} 

@end 

Answer 1

所以我找到了答案，現在我覺得很愚蠢！ 「first」和「last」的使用是保留名稱，不能使用。我將變量更改爲firstName和lastName，它完美地工作。

https://developer.apple.com/library/mac/documentation/Cocoa/Conceptual/Predicates/Articles/pSyntax.html。

謝謝大家的意見和協助。

Answer 2

我有一個NSArray類，可以輕鬆地做這樣的事情：

@interface NSArray (FilterAdditions) 
- (NSArray *)filterObjectsUsingBlock:(BOOL (^)(id obj, NSUInteger idx))block; 
@end 


@implementation NSArray (FilterAdditions) 

- (NSArray *)filterObjectsUsingBlock:(BOOL (^)(id, NSUInteger))block { 
    NSMutableArray *result = [NSMutableArray array]; 
    [self enumerateObjectsUsingBlock:^(id obj, NSUInteger idx, BOOL *stop) { 
     if (block(obj, idx)) { 
      [result addObject:obj]; 
     } 
    }]; 
    return result; 
} 

所以你可以這樣稱呼它：

NSArray *filteredEmployees = 
[employeeList filterObjectsUsingBlock:^BOOL(id obj, NSUInteger idx){ 
    return [(Person2 *)obj.last isEqualToString:@"black"]; 
}];