我的问题：saveInBackground不工作.
原因它不工作：我正在使用NSKeyedArchiving将存储在NSArray中的PFObjects保存到文件中.我这样做的方式是通过这个library实现NSCoding.由于某些原因我不知道,还有其他几个字段被添加并设置为NULL.我有一种感觉,这是把API调用到saveInBackground.当我在第一组对象(NSKeyedArchiving之前)调用saveInBackground时,saveInBackground工作正常.但是,当我把它称为第二个对象(NSKeyedArchiving之后)它不保存.为什么是这样？
保存
[NSKeyedArchiver archiveRootObject:_myArray toFile:[self returnFilePathForType:@"myArray"]];
恢复
_myArray = (NSMutableArray *)[NSKeyedUnarchiver unarchiveObjectWithFile:
[self returnFilePathForType:@"myArray"]];
NSArchiving之前的对象
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>";
}
NSArchiving之后的对象
<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>";
}
更新使用Florent的PFObject类别：
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
解决方法
你得到所有“< null>”的原因NSArchiving之后的条目是因为您使用的NSCoding库的方式处理nil Parse属性.特别是,在2月18日的提交中,处理无效发生了几个变化,包括删除几个测试,以查看属性是否为零,并在解码中添加以下代码：
//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];
}
}
我建议你使用一个替代的NSCoding库.
@AaronBrager在4月22日的答案中建议一个替代图书馆.
更新：
由于替代库缺少对PFFile的支持,下面是您为PFFile实现NSCoding所需的更改的类别实现.简单地编译并添加PFFile NSCoding.m到您的项目.
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：
我已经描述的更新的解决方案(使用Florent’s PFObject / PFACL encoders替换className与parseClassName加上Martin Rybak’s PFFile encoder的组合)可以在下面的测试工具中工作(参见下面的代码),第二次调用saveInBackground调用在从NSKeyedUnarchiver还原后工作.
- (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服务器时,第二次调用saveInBackground创建了新版本的对象.
即使这超出了原始问题的范围,我将看看是否可以鼓励Parse服务器重新保存原始对象.同时请投票和/或接受答案,解决了在NSKeyedArchiving之后使用saveInBackground的问题.
最新更新：
这个问题原来只是一个时间问题 – 当NSKeyedArchiver发生时,第一个saveInBackground没有完成,因此在归档时objectId仍然为零,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)来检测什么时候保存完成,可以调用NSKeyedArchiver也可以工作
以下版本不会导致保存第二个副本：
- (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 (%@): %@",testObject);
testObject = [NSKeyedUnarchiver unarchiveObjectWithFile:[self returnFilePathForType:@"testObject"]];
NSLog(@"Test object after restore: %@",testObject);
// Change the object
testObject[@"foo1"] = @"bar2";
[testObject saveInBackground];
}
} ];
}