我有一个核心数据对象图(由通过一对多关系链接的两个实体组成)。
作为一名相对缺乏经验的iPhone开发人员,我很好奇是否有人能为iPhone推荐一种方法和合适的JSON实现,这将使我能够:
我已经在这一点上搜索了一个教程/代码样本,但没有成功,因此如果有任何帮助,我们将不胜感激。
发布于 2010-03-02 22:55:40
首先,选择一个JSON库来使用,我个人喜欢TouchJSON,但其他几个也很不错。虽然不是很难,但复杂的部分是将托管对象转换为适合转换的结构。我写得很快,所以可能会有一两个错误:)
您调用的方法是:
- (NSString*)jsonStructureFromManagedObjects:(NSArray*)managedObjects;
- (NSArray*)managedObjectsFromJSONStructure:(NSString*)json withManagedObjectContext:(NSManagedObjectContext*)moc;
具体实现如下:
- (NSDictionary*)dataStructureFromManagedObject:(NSManagedObject*)managedObject
{
NSDictionary *attributesByName = [[managedObject entity] attributesByName];
NSDictionary *relationshipsByName = [[managedObject entity] relationshipsByName];
NSMutableDictionary *valuesDictionary = [[managedObject dictionaryWithValuesForKeys:[attributesByName allKeys]] mutableCopy];
[valuesDictionary setObject:[[managedObject entity] name] forKey:@"ManagedObjectName"];
for (NSString *relationshipName in [relationshipsByName allKeys]) {
NSRelationshipDescription *description = [[[managedObject entity] relationshipsByName] objectForKey:relationshipName];
if (![description isToMany]) {
NSManagedObject *relationshipObject = [managedObject valueForKey:relationshipName];
[valuesDictionary setObject:[self dataStructureForManagedObject:relationshipObject] forKey:relationshipName];
continue;
}
NSSet *relationshipObjects = [managedObject objectForKey:relationshipName];
NSMutableArray *relationshipArray = [[NSMutableArray alloc] init];
for (NSManagedObject *relationshipObject in relationshipObjects) {
[relationshipArray addObject:[self dataStructureForManagedObject:relationshipObject]];
}
[valuesDictionary setObject:relationshipArray forKey:relationshipName];
}
return [valuesDictionary autorelease];
}
- (NSArray*)dataStructuresFromManagedObjects:(NSArray*)managedObjects
{
NSMutableArray *dataArray = [[NSMutableArray alloc] init];
for (NSManagedObject *managedObject in managedObjects) {
[dataArray addObject:[self dataStructureForManagedObject:managedObject]];
}
return [dataArray autorelease];
}
- (NSString*)jsonStructureFromManagedObjects:(NSArray*)managedObjects
{
NSArray *objectsArray = [self dataStructuresFromManagedObjects:managedObjects];
NSString *jsonString = [[CJSONSerializer serializer] serializeArray:objectsArray];
return jsonString;
}
- (NSManagedObject*)managedObjectFromStructure:(NSDictionary*)structureDictionary withManagedObjectContext:(NSManagedObjectContext*)moc
{
NSString *objectName = [structureDictionary objectForKey:@"ManagedObjectName"];
NSManagedObject *managedObject = [NSEntityDescription insertNewObjectForEntityForName:objectName inManagedObjectContext:moc];
[managedObject setValuesForKeysWithDictionary:structureDictionary];
for (NSString *relationshipName in [[[managedObject entity] relationshipsByName] allKeys]) {
NSRelationshipDescription *description = [relationshipsByName objectForKey:relationshipName];
if (![description isToMany]) {
NSDictionary *childStructureDictionary = [structureDictionary objectForKey:relationshipName];
NSManagedObject *childObject = [self managedObjectFromStructure:childStructureDictionary withManagedObjectContext:moc];
[managedObject setObject:childObject forKey:relationshipName];
continue;
}
NSMutableSet *relationshipSet = [managedObject mutableSetForKey:relationshipName];
NSArray *relationshipArray = [structureDictionary objectForKey:relationshipName];
for (NSDictionary *childStructureDictionary in relationshipArray) {
NSManagedObject *childObject = [self managedObjectFromStructure:childStructureDictionary withManagedObjectContext:moc];
[relationshipSet addObject:childObject];
}
}
return managedObject;
}
- (NSArray*)managedObjectsFromJSONStructure:(NSString*)json withManagedObjectContext:(NSManagedObjectContext*)moc
{
NSError *error = nil;
NSArray *structureArray = [[CJSONDeserializer deserializer] deserializeAsArray:json error:&error];
NSAssert2(error == nil, @"Failed to deserialize\n%@\n%@", [error localizedDescription], json);
NSMutableArray *objectArray = [[NSMutableArray alloc] init];
for (NSDictionary *structureDictionary in structureArray) {
[objectArray addObject:[self managedObjectFromStructure:structureDictionary withManagedObjectContext:moc]];
}
return [objectArray autorelease];
}
现在,这是递归的,所以如果你不小心,你可以很容易地转换你的整个持久化存储。注意你的关系,并确保它们只在对象树中“向下”移动,这样你才能得到你想要翻译的对象。
发布于 2010-07-19 20:14:09
我只想指出一个小的打字错误,导致代码崩溃,希望这能节省你几分钟的时间。
- (NSArray*)dataStructuresFromManagedObjects:(NSArray*)managedObjects {
NSMutableArray *dataArray = [[NSArray alloc] init];
for (NSManagedObject *managedObject in managedObjects) {
[dataArray addObject:[self dataStructureFromManagedObject:managedObject]];
}
return [dataArray autorelease];
}
The NSMutableArray *dataArray = [[NSArray alloc] init]; // This should be NSMutableArray
真的应该是NSMutableArray *dataArray = [[NSMutableArray alloc] init];
这就是全部。
谢谢
发布于 2010-07-08 04:05:08
Synchronizing Core Data with Rails是一个详细的演示文稿,其中包括将核心数据对象序列化/反序列化到JSON或从JSON反序列化的示例代码(跳到核心数据部分的幻灯片55 )。他的示例代码假设了一个没有关系的相当简单的模型,尽管我认为它很容易扩展。
该演示文稿还详细介绍了如何使核心数据模型与基于REST的web应用程序保持同步,并提供了一些有用的库的指针,包括ObjectiveResource和ASIHTTPRequest。我不确定这是否是你想要做的,但即使是核心数据代码也值得一看。
https://stackoverflow.com/questions/2362323
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