NSCoding 与对象内的 NSString

Posted 2023-02-15

【中文标题】NSCoding 与对象内的 NSString

【英文标题】：NSCoding with as NSString inside a object

【发布时间】：2011-03-28 22:22:38

【问题描述】：

然后我的问题是我检索了 Store 对象的 NSArray，我的所有 NSString 属性都导致 BadAccess 错误。 int 和 double 属性工作正常！

store.h

@interface Store : NSObject<NSCoding> 
    NSString *Name;
    NSString *Address;
    NSString *Phone;
    double GeoLong;
    double GeoLat;
    int ID;         


@property (nonatomic, retain) NSString *Name;
@property (nonatomic, retain) NSString *Address;
@property (nonatomic, retain) NSString *Phone;
@property (nonatomic) double GeoLat;
@property (nonatomic) double GeoLong;
@property (nonatomic) int ID;

@end

store.m

@implementation Store

@synthesize Name;
@synthesize ID;
@synthesize Address;
@synthesize Phone;
@synthesize GeoLat;
@synthesize GeoLong;


/** Implentation of the NSCoding protocol. */

-(void)encodeWithCoder:(NSCoder *)encoder

    [encoder encodeInt:ID forKey:@"ID"];
    [encoder encodeDouble:GeoLat forKey:@"GeoLat"];
    [encoder encodeDouble:GeoLong forKey:@"GeoLong"];
    NSLog(@"Name in encode: %@", Name); //WORKS!
    [encoder encodeObject:Name forKey:@"Name"];
    [encoder encodeObject:Phone forKey:@"Phone"];
    [encoder encodeObject:Address forKey:@"Address"];



-(id)initWithCoder:(NSCoder *)decoder

    // Init first.
    if(self = [self init])

    ID = [decoder decodeIntForKey:@"ID"];
    GeoLat = [decoder decodeDoubleForKey:@"GeoLat"];
    GeoLong = [decoder decodeDoubleForKey:@"GeoLong"];
    Name = [decoder decodeObjectForKey:@"Name"];
    NSLog(@"Name in decode: %@", Name); //WORKS! logs the name

    Address = [decoder decodeObjectForKey:@"Address"];
    Phone = [decoder decodeObjectForKey:@"Phone"];
    

    return self;


- (void)dealloc

    [Name release];
    [ID release];
    [Address release];
    [Phone release];


    [super dealloc];

@end

这是我用于存储和检索数组的代码。

//streams contains the data i will populate my array with. 
for (ndx = 0; ndx < streams.count; ndx++) 
            NSDictionary *stream = (NSDictionary *)[streams objectAtIndex:ndx];

            Store *item = [[Store alloc] init] ;
            item.Name = [stream valueForKey:@"Name"];
            item.Address = [stream valueForKey:@"Address"];
            item.Phone = [stream valueForKey:@"Phone"];
            item.GeoLat = [[stream valueForKey:@"GeoLat"] doubleValue];
            item.GeoLong = [[stream valueForKey:@"GeoLong"] doubleValue];                
            item.ID = [[stream valueForKey:@"ID"] intValue]; 

            [listToReturn addObject:item];
        
    

    //test to check if it works
    for(int i = 0; i < [listToReturn count]; i++)
        Store *item = (Store *)[listToReturn objectAtIndex:i];
        NSLog(@"Name: %@", item.Name); //works
    

    //save
    [[NSUserDefaults standardUserDefaults] setObject:[NSKeyedArchiver archivedDataWithRootObject:listToReturn] forKey:@"stores"];

    // retrieve
    NSMutableArray *stores = [NSMutableArray new];
    NSUserDefaults *currentDefaults = [NSUserDefaults standardUserDefaults];
    NSData *dataRepresentingSavedArray = [currentDefaults objectForKey:@"stores"];
    if (dataRepresentingSavedArray != nil)
    
        NSArray *oldSavedArray = [NSKeyedUnarchiver unarchiveObjectWithData:dataRepresentingSavedArray];
        if (oldSavedArray != nil)
            stores = [[NSMutableArray alloc] initWithArray:oldSavedArray];
        else
            stores = [[NSMutableArray alloc] init];
    

    if ([stores count] > 0) 
        NSMutableArray * annotations =  [[NSMutableArray alloc] init];
        for(int i = 0;i< [stores count]; i++)

            Store *store = [stores objectAtIndex: i];

            CLLocationCoordinate2D location;
            if(store.GeoLat != 0 && store.GeoLong != 0)
                location.latitude = store.GeoLat;
                location.longitude = store.GeoLong; //works 
                NSLog(@"Adding store: %@", store.Name); //DONT WORK!! <-- MAIN PROBLEM
            
        
    

感觉我什么都试过了，但不知道它在解码中是如何工作的，但在我把它放入数组后循环数组时却不知道。

有人有什么想法吗？

【问题讨论】：

嘿，我意识到这与手头的问题无关，只是仅供参考。以大写字母开头的变量名违反了所有样式指南。

在objective-c中，您的ivars应该在第一个字母上使用小写字母，而类应该在第一个字母上使用大写字母......只是一个约定。

【参考方案1】：

您没有保留initWithCoder 中的属性。

Name = [decoder decodeObjectForKey:@"Name"];

没有使用您定义的（保留）属性的设置器。您只是在设置 ivar。这意味着您不会获得所有权，并且可以将其解除分配。

您可以通过以下两种方式保留案例中的属性：

self.Name = [decoder decodeObjectForKey:@"Name"];
Name = [[decoder decodeObjectForKey:@"Name"] retain];

【讨论】：

太棒了，太棒了，你也是 :)

良好而丰富的解释 :) 正是我想要的 :)