如何将字典从NSString初始化为NSArray

Question

我试图创建一个字典(不确定它是否应该NSDictionary或NSMutableDictionary)从NSString一个数组(不确定它是否应该NSArray或NSMutableArray).

属性:

@property(nonatomic, readonly) NSMutableDictionary * categories;

执行:

@synthesize categories = _categories;


- (NSMutableDictionary *)categories{
    if(! _categories) {
        for(PFObject * each in self.products) {
            NSString * currentcategory = [each valueForKey:@"subtitle"];
            NSArray * currentlist = [_categories objectForKey:currentcategory];
            if(! currentlist) {
                currentlist = [[NSArray alloc] init];
            }
            NSMutableArray * newArray = [currentlist mutableCopy];
            [newArray addObject:each];
            NSArray * newlist = [NSArray arrayWithArray:newArray];
            [_categories setObject:newlist forKey:currentcategory];
        }
    }
    NSLog(@"After constructor the value of the dictionary is %d", [_categories count]);
    return _categories;
}

从调试NSLog我发现构造后字典是空的.这里有什么问题,我该如何改变呢？

Answer 1

代码行之后

 if(! _categories) {

加

_categories = [NSMutableDictionary new];