Ios 将带有自定义对象的NSDictionary写入文件

我有一个带有自定义对象数组的

NSDictionary

，名为

MAClass

es。我尝试将dict写入文件，这是一种简单的方法：

- (void)writeDictToFileWithContent:(NSDictionary *)contentDict {
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    NSString *filePath = [documentsDirectory stringByAppendingPathComponent:@"/userdata.txt"];


    [contentDict writeToFile:filePath atomically:YES];

}

然后我用

- (NSDictionary *)readFromDict {
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    NSString *filePath = [documentsDirectory stringByAppendingPathComponent:@"/userdata.txt"];

    NSDictionary *contentDict = [NSDictionary dictionaryWithContentsOfFile:filePath];

    return contentDict;
}

我试图编写的对象数组是一个自定义NSObject，其结构类似于：

@interface MAAssignment : NSObject

@property (nonatomic, strong) NSDate *date;
@property (nonatomic, strong) NSString *assignmentName;
@property (nonatomic, strong) NSNumber *totalPoints;
@property (nonatomic, strong) NSNumber *recievedPoints;
@property (nonatomic, strong) NSNumber *classAverage;
@property (nonatomic, strong) NSNumber *extraCredit;
@property (nonatomic, strong) NSNumber *notGraded;

它代表一个类

我以前只使用NSString和NSNumber的数组，它可以很好地读写。当我切换MAClass对象时，当我尝试读取时，它返回一个空的dict

这可能就是为什么：

---

我该怎么写dict呢？

你需要序列化你的自定义对象，一种方法是，在你的自定义类中，编写以下两个方法，对你想要保存的每个属性进行编码/解码，然后我不确定writeToFile是否真的会使用它，但我知道您可以从对象创建NSData，并使用以下方法将其写入文件

     //archive dictionary and serializable objects to NSData  
     NSData *serializedData= [NSKeyedArchiver archivedDataWithRootObject:myDict];

//Unarchive 
    NSData *myData=[NSData dataWithContentsOfFile:appFile];

    NSMutableDictionary* myDict= (NSMutableDictionary*)[NSKeyedUnarchiver unarchiveObjectWithData:myData];

以下是自定义对象中需要的两种方法：

- (void)encodeWithCoder:(NSCoder *)coder
{
    [coder encodeInt:self.propOne forKey:@"PropOne"];
    [coder encodeObject:self.propTwo forKey:@"PropTwo"];
    ...

}
// Decode an object from an archive
- (id)initWithCoder:(NSCoder *)coder
{
    self = [super init];
    self.propOne=[coder decodeIntegerForKey:@"PropOne"];
    self.propTwo=[coder decodeObjectForKey:@"PropTwo"];
     ..

    return self;
}

---

希望对您有所帮助

您无法使用自定义对象保存nsdictionary。尝试将nsdictionary以编码形式保存到文件中并检索词典，然后对其进行解码。那我想你会得到你的目标的。 试试这个

- (void)writeDictToFileWithContent:(NSDictionary *)contentDict {
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    NSString *filePath = [documentsDirectory stringByAppendingPathComponent:@"/userdata.txt"];

 NSData *data = [NSKeyedArchiver archivedDataWithRootObject:contentDict]; 
    [data writeToFile:filePath atomically:YES];


}

- (NSDictionary *)readFromDict {
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES);
    NSString *documentsDirectory = [paths objectAtIndex:0];
    NSString *filePath = [documentsDirectory stringByAppendingPathComponent:@"/userdata.txt"];

    NSDictionary *contentDict = [NSDictionary dictionaryWithContentsOfFile:filePath];


    return [NSKeyedUnarchiver unarchiveObjectWithData:contentDict];;
}

---

-[MAClass encodeWithCoder:]：发送到实例0xba92af0的无法识别的选择器

我是否需要在my

MAClass

NSObject中添加一个encode WithCoder方法？是的，您还必须实现这些方法，或者您必须从文件中读取存档数据是NSData*storedData=[NSData data WITHCONTENTSOFILE:[self myDataFilePath]]; 返回[NSKeyedUnarchiver unarchiveObjectWithData:storedData]；您建议如何制作对象和INT？我不完全理解整个

PropOne

，

PropTwo

。@user3451350 PropOne/PropTwo是你的类的属性，我只是把它们命名为示例…

-（void）encodeWithCoder:（NSCoder*）encoder{[encoder-encoder-object:self-forKey:@“self”；}

-（id）initWithCoder:（NSCoder*））解码器{if（self=[super init]）{self=[decoder decodeObjectForKey:@“self”]；}返回self；}

这些方法有效吗？？？@user3451350不，你不能解码self…你的对象中有属性，你在问题中列出了它们，现在只需写一行[coder-encodeObject:self.propTwo-forKey:@“PropTwo”]；对于每个属性（您的所有属性都是对象），顺便说一句，您的属性是日期、分配名称、总点数等