拯救PFObject NSCoding

Question

我的问题： saveInBackground没有工作。

不起作用的原因是：，我将存储在NSArray中的PFObjects保存为使用NSKeyedArchiving进行文件处理。我这样做的方法是通过这个NSCoding实现图书馆。由于一些我不知道的原因，正在添加其他几个字段，并将其设置为NULL。我有一种感觉，这是搞砸了对saveInBackground的API调用。当我对第一组对象(在saveInBackground之前)调用NSKeyedArchiving时，saveInBackground工作得很好。但是，当我对第二个对象(在NSKeyedArchiving之后)调用它时，它不会保存。为什么会这样呢？

Save

[NSKeyedArchiver archiveRootObject:_myArray toFile:[self returnFilePathForType:@"myArray"]];

检索

_myArray = (NSMutableArray *)[NSKeyedUnarchiver unarchiveObjectWithFile:
                                             [self returnFilePathForType:@"myArray"]];

对象在NSArchiving之前

2014-04-16 16:34:56.267 myApp[339:60b]
<UserToMessage:bXHfPM8sDs:(null)> {
    from = "<PFUser:sdjfa;lfj>";
    messageText = "<MessageText:asdffafs>";
    read = 0;
    to = "<PFUser:asdfadfd>";
}
2014-04-16 16:34:56.841 myApp[339:60b]
<UserToMessage:bXHsdafdfs:(null)> {
    from = "<PFUser:eIasdffoF3gi>";
    messageText = "<MessageText:asdffafs>";
    read = 1;
    to = "<PFUser:63sdafdf5>";
}

对象在NSArchiving之后

<UserToMessage:92GGasdffVQLa:(null)> {
    ACL = "<null>";
    createdAt = "<null>";
    from = "<PFUser:eIQsadffF3gi>";
    localId = "<null>";
    messageText = "<MessageText:EudsaffdHpc>";
    objectId = "<null>";
    parseClassName = "<null>";
    read = 0;
    saveDelegate = "<null>";
    to = "<PFUser:63spasdfsxNp5>";
    updatedAt = "<null>";
}

2014-04-16 16:37:46.527 myApp[352:60b]
<UserToMessage:92GadfQLa:(null)> {
    ACL = "<null>";
    createdAt = "<null>";
    from = "<PFUser:eIQsadffF3gi>";
    localId = "<null>";
    messageText = "<MessageText:EuTndasHpc>";
    objectId = "<null>";
    parseClassName = "<null>";
    read = 1;
    saveDelegate = "<null>";
    to = "<PFUser:63spPsadffp5>";
    updatedAt = "<null>";
}

使用Florent的PFObject类别更新：

PFObject+MyPFObject_NSCoding.h

#import <Parse/Parse.h>

@interface PFObject (MyPFObject_NSCoding)

-(void) encodeWithCoder:(NSCoder *) encoder;
-(id) initWithCoder:(NSCoder *) aDecoder;
@end

@interface PFACL (extensions)
-(void) encodeWithCoder:(NSCoder *) encoder;
-(id) initWithCoder:(NSCoder *) aDecoder;
@end


 PFObject+MyPFObject_NSCoding.m

#import "PFObject+MyPFObject_NSCoding.h"
@implementation PFObject (MyPFObject_NSCoding)
#pragma mark - NSCoding compliance
#define kPFObjectAllKeys @"___PFObjectAllKeys"
#define kPFObjectClassName @"___PFObjectClassName"
#define kPFObjectObjectId @"___PFObjectId"
#define kPFACLPermissions @"permissionsById"
-(void) encodeWithCoder:(NSCoder *) encoder{

    // Encode first className, objectId and All Keys
    [encoder encodeObject:[self className] forKey:kPFObjectClassName];
    [encoder encodeObject:[self objectId] forKey:kPFObjectObjectId];
    [encoder encodeObject:[self allKeys] forKey:kPFObjectAllKeys];
    for (NSString * key in [self allKeys]) {
        [encoder  encodeObject:self[key] forKey:key];
    }


}
-(id) initWithCoder:(NSCoder *) aDecoder{

    // Decode the className and objectId
    NSString * aClassName  = [aDecoder decodeObjectForKey:kPFObjectClassName];
    NSString * anObjectId = [aDecoder decodeObjectForKey:kPFObjectObjectId];


    // Init the object
    self = [PFObject objectWithoutDataWithClassName:aClassName objectId:anObjectId];

    if (self) {
        NSArray * allKeys = [aDecoder decodeObjectForKey:kPFObjectAllKeys];
        for (NSString * key in allKeys) {
            id obj = [aDecoder decodeObjectForKey:key];
            if (obj) {
                self[key] = obj;
            }

        }
    }
    return self;
}
@end

Answer 1

我创建了一个非常简单的解决方案，不需要更改上面的NSCoding库：

PFObject *tempRelationship = [PFObject objectWithoutDataWithClassName:@"relationship" objectId:messageRelationship.objectId];
        [tempRelationship setObject:[NSNumber numberWithBool:YES] forKey:@"read"];
        [tempRelationship saveInBackgroundWithBlock:^(BOOL succeeded, NSError *error) {
            if (succeeded)
                NSLog(@"Success");
            else
                NSLog(@"Error");
        }];

我们在这里要做的是使用相同的objectId创建一个临时对象，并保存它。这是一个工作解决方案，不会在服务器上创建对象的副本。感谢所有帮助过的人。

Answer 2

在"<null>"之后获取所有NSArchiving条目的原因是您使用的NSCoding库处理零解析属性的方式。特别是，在2月18日的提交中，对nil的处理发生了一些更改，包括删除了几个测试，以查看属性是否为零，并在解码中添加了以下代码：

    //Deserialize each nil Parse property with NSNull
    //This is to prevent an NSInternalConsistencyException when trying to access them in the future
    for (NSString* key in [self dynamicProperties]) {
        if (![allKeys containsObject:key]) {
            self[key] = [NSNull null];
        }
    }

我建议您使用另一个NSCoding库。

@AaronBrager在4月22日的答复中提出了另一个图书馆。

更新：

由于替代库缺少对PFFile的支持，下面是实现NSCoding for PFFile所需更改的类别实现。只需将PFFile+NSCoding.m编译并添加到项目中即可。此实现来自您使用的原始NSCoding库。

PFFile+NSCoding.h

//
//  PFFile+NSCoding.h
//  UpdateZen
//
//  Created by Martin Rybak on 2/3/14.
//  Copyright (c) 2014 UpdateZen. All rights reserved.
//

#import <Parse/Parse.h>

@interface PFFile (NSCoding)

- (void)encodeWithCoder:(NSCoder*)encoder;
- (id)initWithCoder:(NSCoder*)aDecoder;

@end

PFFile+NSCoding.m

//
//  PFFile+NSCoding.m
//  UpdateZen
//
//  Created by Martin Rybak on 2/3/14.
//  Copyright (c) 2014 UpdateZen. All rights reserved.
//

#import "PFFile+NSCoding.h"
#import <objc/runtime.h>

#define kPFFileName @"_name"
#define kPFFileIvars @"ivars"
#define kPFFileData @"data"

@implementation PFFile (NSCoding)

- (void)encodeWithCoder:(NSCoder*)encoder
{
    [encoder encodeObject:self.name forKey:kPFFileName];
    [encoder encodeObject:[self ivars] forKey:kPFFileIvars];
    if (self.isDataAvailable) {
        [encoder encodeObject:[self getData] forKey:kPFFileData];
    }
}

- (id)initWithCoder:(NSCoder*)aDecoder
{
    NSString* name = [aDecoder decodeObjectForKey:kPFFileName];
    NSDictionary* ivars = [aDecoder decodeObjectForKey:kPFFileIvars];
    NSData* data = [aDecoder decodeObjectForKey:kPFFileData];

    self = [PFFile fileWithName:name data:data];
    if (self) {
        for (NSString* key in [ivars allKeys]) {
            [self setValue:ivars[key] forKey:key];
        }
    }
    return self;
}

- (NSDictionary *)ivars
{
    NSMutableDictionary* dict = [[NSMutableDictionary alloc] init];
    unsigned int outCount;

    Ivar* ivars = class_copyIvarList([self class], &outCount);
    for (int i = 0; i < outCount; i++){
        Ivar ivar = ivars[i];
        NSString* ivarNameString = [NSString stringWithUTF8String:ivar_getName(ivar)];
        NSValue* value = [self valueForKey:ivarNameString];
        if (value) {
            [dict setValue:value forKey:ivarNameString];
        }
    }

    free(ivars);
    return dict;
}

@end

第二次更新：

我所描述的更新解决方案(使用Florent's PFObject / PFACL编码器将className替换为parseClassName + 马丁·雷巴克的PFFile编码器)确实有效--在下面的测试工具中(请参阅下面的代码)，对saveInBackground调用的第二个调用在从NSKeyedUnarchiver进行恢复之后才能工作。

- (void)viewDidLoad {
    [super viewDidLoad];

    PFObject *testObject = [PFObject objectWithClassName:@"TestObject"];
    testObject[@"foo1"] = @"bar1";
    [testObject saveInBackground];

    BOOL success = [NSKeyedArchiver archiveRootObject:testObject toFile:[self returnFilePathForType:@"testObject"]];
    NSLog(@"Test object after archive (%@): %@", (success ? @"succeeded" : @"failed"), testObject);

    testObject = [NSKeyedUnarchiver unarchiveObjectWithFile:[self returnFilePathForType:@"testObject"]];
    NSLog(@"Test object after restore: %@", testObject);

    // Change the object
    testObject[@"foo1"] = @"bar2";
    [testObject saveInBackground];
}

- (NSString *)returnFilePathForType:(NSString *)param {
    NSString *docDir = [NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) objectAtIndex:0];
    NSString *filePath = [docDir stringByAppendingPathComponent:[param stringByAppendingString:@".dat"]];

    return filePath;
}

但是，查看Parse服务器，对saveInBackground的第二次调用创建了该对象的新版本。

即使这超出了最初问题的范围，我还是要看看是否有可能鼓励Parse服务器重新保存原始对象。同时，请投票和/或接受答案，因为它解决了在NSKeyedArchiving之后使用NSKeyedArchiving的问题。

最终更新：

这个问题原来只是一个时间问题--第一个saveInBackground在NSKeyedArchiver发生时还没有完成--因此在归档时objectId仍然是零，因此在第二个saveInBackground时仍然是一个新对象。使用一个块(类似于下面)来检测保存何时完成，调用NSKeyedArchiver也是可以的。

以下版本不会导致保存第二份副本：

- (void)viewDidLoad {
    [super viewDidLoad];

    __block PFObject *testObject = [PFObject objectWithClassName:@"TestObject"];
    testObject[@"foo1"] = @"bar1";
    [testObject saveInBackgroundWithBlock:^(BOOL succeeded, NSError *error) {
        if (succeeded) {
            BOOL success = [NSKeyedArchiver archiveRootObject:testObject toFile:[self returnFilePathForType:@"testObject"]];
            NSLog(@"Test object after archive (%@): %@", (success ? @"succeeded" : @"failed"), testObject);

            testObject = [NSKeyedUnarchiver unarchiveObjectWithFile:[self returnFilePathForType:@"testObject"]];
            NSLog(@"Test object after restore: %@", testObject);

            // Change the object
            testObject[@"foo1"] = @"bar2";
            [testObject saveInBackground];
        }
    } ];

}

Answer 3

PFObject没有实现NSCoding，而且您使用的库似乎没有正确地编码对象，因此您的当前方法无法工作。

Parse建议的方法是通过设置PFQuery属性将您的cachePolicy对象缓存到磁盘上：

PFQuery *query = [PFQuery queryWithClassName:@"GameScore"];
query.cachePolicy = kPFCachePolicyNetworkElseCache;
[query findObjectsInBackgroundWithBlock:^(NSArray *objects, NSError *error) {
  if (!error) {
    // Results were successfully found, looking first on the
    // network and then on disk.
  } else {
    // The network was inaccessible and we have no cached data for
    // this query.
  }
}];

(来自缓存查询文档的代码。)

然后你的应用程序将从缓存加载。如果您想先尝试磁盘缓存(速度更快，但可能已经过时)，请切换到kPFCachePolicyCacheElseNetwork。

查询对象的maxCacheAge属性设置了某些东西在过期前将在磁盘上停留多久。

或者，这里有弗洛伦特的PFObject分类向PFObject添加NSCoder支持。它不同于您链接到的库中的实现，但我不确定它有多可靠。这可能是值得尝试的。