符合nscoding的对象将不会写入文件 [英] objects conforming to nscoding will not writetofile

问题描述

我想将一个Question对象数组写入文件，但是以某种方式writeToFile没有做任何事情.一个问题有一个所有者和一个答案对象数组.答案也有一个所有者.他们三个都符合NSCoding协议(据我所知).

I want to write an array of Question objects to file, but somehow writeToFile isn't doing anything. A Question has an Owner and and an array of Answer objects. An Answer has an Owner as well. All three of them conform to the NSCoding protocol (as far as I know).

从下面的代码中，结果返回NO.不知道我在做什么错，因为我正在为所有内容实施NSCoding，对吗?

From the code below, result returns NO. No clue what I'm doing wrong, since I am implementing NSCoding for everything, right?

Question.h

#import <Foundation/Foundation.h>
#import "Owner.h"

@interface Question : NSObject <NSCoding> {
    NSString *questionId;
    NSString *questionRevision;
    NSString *text;
    NSDate *date;
    NSMutableArray *answers;
    NSString *page;
    NSNumber *questionLocation;

    Owner *owner;
}

@property (nonatomic, retain) NSString *questionId;
@property (nonatomic, retain) NSString *questionRevision;
@property (nonatomic, retain) NSString *text;
@property (nonatomic, retain) NSDate *date;
@property (nonatomic, retain) NSMutableArray *answers;
@property (nonatomic, retain) NSString *page;
@property (nonatomic, retain) NSNumber *questionLocation;
@property (nonatomic, retain) Owner *owner;

@end

Question.m

#import "Question.h"
#import "Answer.h"

@implementation Question

@synthesize questionId, questionRevision, text, date, answers, page, questionLocation, owner;

- (void)encodeWithCoder:(NSCoder *)coder
{
    //[super encodeWithCoder:coder];
    [coder encodeObject:questionId forKey:@"questionId"];
    [coder encodeObject:questionRevision forKey:@"questionRevision"];
    [coder encodeObject:text forKey:@"text"];
    [coder encodeObject:date forKey:@"date"];
    [coder encodeObject:answers forKey:@"answers"];
    [coder encodeObject:page forKey:@"page"];
    [coder encodeObject:questionLocation forKey:@"questionLocation"];
    [coder encodeObject:owner forKey:@"owner"];
}

- (id)initWithCoder:(NSCoder *)decoder
{
    //self = [super initWithCoder:decoder];
    self = [super init];
    self.questionId = [decoder decodeObjectForKey:@"questionId"];
    self.questionRevision = [decoder decodeObjectForKey:@"questionRevision"];
    self.text = [decoder decodeObjectForKey:@"text"];
    self.date = [decoder decodeObjectForKey:@"date"];
    self.answers = [decoder decodeObjectForKey:@"answers"];
    self.page = [decoder decodeObjectForKey:@"page"];
    self.questionLocation = [decoder decodeObjectForKey:@"questionLocation"];
    self.owner = [decoder decodeObjectForKey:@"owner"];
}

@end

Answer.h

#import <Foundation/Foundation.h>
#import "Owner.h"

@interface Answer : NSObject <NSCoding> {
    Owner *owner;
    NSString *text;
    NSDate *date;
}

@property (nonatomic, retain) Owner *owner;
@property (nonatomic, retain) NSString *text;
@property (nonatomic, retain) NSDate *date;

@end

答案

#import "Answer.h"


@implementation Answer

@synthesize owner, text, date;

    - (void)encodeWithCoder:(NSCoder *)coder
    {
    //[super encodeWithCoder:coder];
    [coder encodeObject:owner forKey:@"owner"];
    [coder encodeObject:text forKey:@"text"];
    [coder encodeObject:date forKey:@"date"];
}

- (id)initWithCoder:(NSCoder *)decoder
{
    //self = [super initWithCoder:decoder];
    self = [super init];
    self.owner = [decoder decodeObjectForKey:@"owner"];
    self.text = [decoder decodeObjectForKey:@"text"];
    self.date = [decoder decodeObjectForKey:@"date"];
}

@end

Owner.h

#import <Foundation/Foundation.h>


@interface Owner : NSObject <NSCoding> {
    NSString *name;
    NSString *photoFileName;
}

@property (nonatomic, retain) NSString *name;
@property (nonatomic, retain) NSString *photoFileName;

@end

Owner.m

#import "Owner.h"


@implementation Owner

@synthesize name, photoFileName;

- (void)encodeWithCoder:(NSCoder *)coder
{
    //[super encodeWithCoder:coder];
    [coder encodeObject:name forKey:@"name"];
    [coder encodeObject:photoFileName forKey:@"photoFileName"];
}

- (id)initWithCoder:(NSCoder *)decoder
{
    //self = [super initWithCoder:decoder];
    self = [super init];
    self.name = [decoder decodeObjectForKey:@"name"];
    self.photoFileName = [decoder decodeObjectForKey:@"photoFileName"];
}

@end

相关代码行
BOOL result = [questions writeToFile:@"Users/brunoscheele/Desktop/questions.plist" atomically:YES];

推荐答案

writeToFile:atomically:写入属性列表文件，而不是序列化存档.无法通过实现NSCoding来扩展属性列表类型，并且由于您的对象不是属性列表支持的类型之一，因此无法将它们写入属性列表.

writeToFile:atomically: writes property list files, not serialised archives. Property list types can't be extended by implementing NSCoding, and as your objects aren't one of the types supported by property lists, then they can't be written to a property list.

要存档对象，您需要使用NSAchiver，例如:

To archive your objects, you'll need to use an NSAchiver, for example:

[NSKeyedArchiver archiveRootObject:questions 
                 toFile:@"some/path/questions.archive"]

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