在iOS中保存/序列化自定义对象的正确方法

Question

我有一个自定义对象，UIImageView子类有几个gestureRecognizer对象。

如果我有一些这些对象存储在NSMutableArray，这个对象的数组将如何保存到磁盘，以便它可以在用户再次运行应用程序时加载？我想从磁盘加载数组，并使用对象。

Answer 1

我类似的东西，实现以下和完美的作品：

自定义对象（设置）应实现协议NSCoding：

-(void)encodeWithCoder:(NSCoder *)encoder{ 
    [encoder encodeObject:self.difficulty forKey:@"difficulty"]; 
    [encoder encodeObject:self.language forKey:@"language"]; 
    [encoder encodeObject:self.category forKey:@"category"]; 
    [encoder encodeObject:self.playerType forKey:@"playerType"]; 
} 

- (id)initWithCoder:(NSCoder *)decoder { 
    if (self = [super init]) { 
     self.difficulty = [decoder decodeObjectForKey:@"difficulty"]; 
     self.language = [decoder decodeObjectForKey:@"language"]; 
     self.category = [decoder decodeObjectForKey:@"category"]; 
     self.playerType = [decoder decodeObjectForKey:@"playerType"]; 
    } 
    return self; 
} 

下面的代码将自定义对象到一个文件中（ set.txt），然后将其恢复到阵列myArray：

NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); 
NSString *documentsDirectory = [paths objectAtIndex:0]; 
NSString *appFile = [documentsDirectory stringByAppendingPathComponent:@"set.txt"]; 

NSMutableArray *myObject=[NSMutableArray array]; 
[myObject addObject:self.settings];  

[NSKeyedArchiver archiveRootObject:myObject toFile:appFile]; 

NSMutableArray* myArray = [NSKeyedUnarchiver unarchiveObjectWithFile:appFile]; 

Answer 2

本博客文章解释了如何使用NSKeyedArchiver存储自定义对象的数组到磁盘，并与NSKeyedUnarchiver读回：

http://www.cocoabuilder.com/archive/cocoa/240775-saving-nsarray-of-custom-objects.html

苹果也有对此事进行了非常有益的指导，Archives and Serializations Programming Guide。

Answer 3

//store the array 
[NSKeyedArchiver archiveRootObject:myArray toFile:@"someFile"]; 

//load the array 
NSMutableArray* myArray = [NSKeyedUnarchiver unarchiveObjectWithFile:@"someFile"]; 

Official References。

请注意，当数组包含自定义对象类型时，必须确保类型符合NSCoding Protocol，然后才能使用。

Answer 4

我想分享我对Kostas解决方案的改进，如果someb ody需要他们。

1. 类名可用于生成文本文件名来存储对象。
2. 这是一个很好的解决方案，可以在viewWillDisappear方法中保存视图控制器的对象，并在viewDidLoad方法中恢复它们。
3. 文件名应该在单独的方法中生成以避免重复的代码。
4. 恢复对象后，应该检查为不是零。

---

- (void)viewDidLoad 
{ 
    [super viewDidLoad]; 

    // Restoring form object from the file 
    NSString *formFilePath = [self formFilePath]; 
    RRCreateResumeForm *form = [NSKeyedUnarchiver unarchiveObjectWithFile:formFilePath]; 
    if (form != nil) { 
    self.formController.form = form; 
    } 
} 


- (void)viewWillDisappear:(BOOL)animated 
{ 
    [super viewWillDisappear:animated]; 

    // Saving the form object to the file 
    NSString *formFilePath = [self formFilePath]; 
    [NSKeyedArchiver archiveRootObject:self.formController.form toFile:formFilePath]; 
} 


// Returns a file path to the file with stored form data for form controller 
- (NSString *)formFilePath 
{ 
    NSArray *paths = NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES); 
    NSString *documentsDirectory = [paths objectAtIndex:0]; 
    NSString *formClassName = NSStringFromClass([self.formController.form class]); 
    NSString *formFileName = [NSString stringWithFormat:@"%@.txt", formClassName]; 
    NSString *formFilePath = [documentsDirectory stringByAppendingPathComponent:formFileName]; 

    return formFilePath; 
}