将NSArray转换为NSDictionary

Question

我怎么能转换的NSArray一种NSDictionary,通过阵列的对象的一个int领域作为重点NSDictionary？

Answer 1

试试这个魔法:

NSDictionary *dict = [NSDictionary dictionaryWithObjects:records 
                                   forKeys:[records valueForKey:@"intField"]];

仅供参考,因为这个内置功能:

@interface NSArray(NSKeyValueCoding)

/* Return an array containing the results of invoking -valueForKey: 
on each of the receiver's elements. The returned array will contain
NSNull elements for each instance of -valueForKey: returning nil.
*/
- (id)valueForKey:(NSString *)key;

Answer 2

- (NSDictionary *) indexKeyedDictionaryFromArray:(NSArray *)array 
{
  id objectInstance;
  NSUInteger indexKey = 0U;

  NSMutableDictionary *mutableDictionary = [[NSMutableDictionary alloc] init];
  for (objectInstance in array)
    [mutableDictionary setObject:objectInstance forKey:[NSNumber numberWithUnsignedInt:indexKey++]];

  return (NSDictionary *)[mutableDictionary autorelease];
}

Answer 3

这会添加类别扩展名NSArray.需要C99模式(这是默认情况,但以防万一).

在一个.h可以#import由所有人编辑的文件中..

@interface NSArray (indexKeyedDictionaryExtension)
- (NSDictionary *)indexKeyedDictionary
@end

在一个.m文件..

@implementation NSArray (indexKeyedDictionaryExtension)

- (NSDictionary *)indexKeyedDictionary
{
  NSUInteger arrayCount = [self count];
  id arrayObjects[arrayCount], objectKeys[arrayCount];

  [self getObjects:arrayObjects range:NSMakeRange(0UL, arrayCount)];
  for(NSUInteger index = 0UL; index < arrayCount; index++) { objectKeys[index] = [NSNumber numberWithUnsignedInteger:index]; }

  return([NSDictionary dictionaryWithObjects:arrayObjects forKeys:objectKeys count:arrayCount]);
}

@end

使用示例:

NSArray *array = [NSArray arrayWithObjects:@"zero", @"one", @"two", NULL];
NSDictionary *dictionary = [array indexKeyedDictionary];

NSLog(@"dictionary: %@", dictionary);

输出:

2009-09-12 08:41:53.128 test[66757:903] dictionary: {
    0 = zero;
    1 = one;
    2 = two;
}