ios - 如何在其他方法中访问字典？

Question

下面是我用来尝试使用另一种方法访问初始化字典的代码:

#import "UserFoodData.h"

@implementation UserFoodData

-(void)loadUserFoodData{
    NSString *appDataPath = [[NSBundle mainBundle] pathForResource:@"UserFoodData"     ofType:@"plist"];
    NSMutableDictionary *userFoodDictionary = [[NSMutableDictionary alloc]     initWithContentsOfFile:appDataPath];

    for (userFoodDictionary in userFoodDictionary){
        NSLog(@"%@", userFoodDictionary);
    }

}

-(void)setName:(NSString *)foodName andCarbs:(NSNumber *)carbAmount{
    [userFoodDictionary setObject:foodName forKey:foodName];

}

@end

我似乎收到的错误消息是: 使用未声明的标识符“userFoodDictionary”

现在我认为错误的是，编译器认为 setName:andCarbs 方法有可能在应用程序主屏幕初始化时调用的 loadUserFoodData 之前执行。有人可以帮我解决这个问题吗？

Answer 1

我似乎得到的错误信息是:

使用未声明的标识符“userFoodDictionary”

编译器说:

<强>1。我没有在本地看到任何变量，例如 userFoodDictionary 或 -(void)setName:(NSString *)foodName andCarbs:(NSNumber *)carbAmount 中的实例变量。

<强>2。但您正在尝试访问它。

 and also your for loop has mistakes. please verify my answer

编译器正在尝试在“UserFoodData”类中查找 userFoodDictionary。因为您正在 loadUserFoodData 方法之外访问 userFoodDictionary。因此，为了访问本地方法之外的内容，您必须将该引用保存在头文件中，然后您可以在类中的任何位置访问它。

@interface UserFoodData : NSObject

@property(nonatomic,retain)NSMutableDictionary *userFoodDictionary;

@end

#import "UserFoodData.h"

@implementation UserFoodData
//@synthesize userFoodDictionary; synthesise is automatically entered by compiler

-(void)loadUserFoodData{
    NSString *appDataPath = [[NSBundle mainBundle] pathForResource:@"UserFoodData"     ofType:@"plist"];

    self.userFoodDictionary = [[NSMutableDictionary alloc]     initWithContentsOfFile:appDataPath];

//Please not down this
    for (id aFood in userFoodDictionary){
        NSLog(@"%@", aFood);
    }

}

-(void)setName:(NSString *)foodName andCarbs:(NSNumber *)carbAmount{
    [self.userFoodDictionary setObject:foodName forKey:foodName];

}

@end