我的问题:saveInBackground 不工作。
它不起作用的原因:我正在使用 NSKeyedArchiving 将存储在 NSArray 中的 PFObjects 保存到文件中。我这样做的方法是通过这个 library 实现 NSCoding .由于某种我不知道的原因，正在添加其他几个字段并将其设置为 NULL。我有一种感觉，这会搞砸对 saveInBackground 的 API 调用。当我在第一组对象上调用 saveInBackground 时(在 NSKeyedArchiving 之前)saveInBackground 工作得很好。但是，当我在第二个对象上调用它时(在 NSKeyedArchiving 之后)它不会保存。这是为什么？
保存
[NSKeyedArchiver archiveRootObject:_myArray toFile:[self returnFilePathForType:@"myArray"]];
检索
_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 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>";
}
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
最佳答案
您获得所有 "<null>" 的原因NSArchiving 之后的条目是因为您使用的 NSCoding 库处理 nil Parse 属性的方式。特别是，在 2 月 18 日的一次提交中，对 nil 的处理发生了一些变化，包括删除了几个检查属性是否为 nil 的测试，以及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];
}
}
我建议您使用替代的 NSCoding 库。
@AaronBrager 在 4 月 22 日的回答中建议了一个替代库。
更新:
由于替代库缺少对 PFFile 的支持，下面是为 PFFile 实现 NSCoding 所需的更改的类别实现。只需编译并添加 PFFile+NSCoding.m到你的项目。
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:
我描述的更新解决方案(使用 Florent's PFObject / PFACL encoders 的组合替换 className 与 parseClassName 加上 Martin Rybak's PFFile encoder )确实有效 - 在下面的测试工具中(见下面的代码)第二次调用 saveInBackground从 NSKeyedUnarchiver 恢复后调用确实有效.
- (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，第二次调用 saveInBackground已创建对象的新版本。
即使这超出了原始问题的范围，我也会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，因为它解决了使用 saveInBackground 的问题。在 NSKeyedArchiving 之后.
最终更新:
这个问题原来只是一个时间问题 - 当 NSKeyedArchiver 发生时第一次 saveInBackground 还没有完成 - 因此在归档时 objectId 仍然是 nil，因此在第二次 saveInBackground 时它仍然是一个新对象.使用一个 block (类似于下面)来检测何时保存完成并且可以调用 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 (%@): %@", (success ? @"succeeded" : @"failed"), testObject);
testObject = [NSKeyedUnarchiver unarchiveObjectWithFile:[self returnFilePathForType:@"testObject"]];
NSLog(@"Test object after restore: %@", testObject);
// Change the object
testObject[@"foo1"] = @"bar2";
[testObject saveInBackground];
}
} ];
}
关于ios - 保存 PFObject NSCoding，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/23119739/