iphone - initWithCoder 用于加载 xib 示例

Question

我正在阅读有关从 XIB 文件初始化存档对象的信息，并发现

- (id)initWithCoder:(NSCoder *)aDecoder 

是一种方法。但我无法解决这个问题。有人可以告诉我一个简单的例子来说明如何做到这一点吗？

万分感谢

Answer 1

该类NSCoder用于archive/unarchive（编组/解组，序列化/反序列化）的objects.

这是一种在流（如文件、套接字）上写入对象并能够稍后或在不同位置检索它们的方法。

我建议您阅读存档

您还需要定义如下方法：

- (void)encodeWithCoder:(NSCoder *)enCoder 
{ 
    [super encodeWithCoder:enCoder];

    [enCoder encodeObject:instanceVariable forKey:INSTANCEVARIABLE_KEY];

    // Similarly for the other instance variables.
    ....
}

并在 initWithCoder 方法中初始化如下：

- (id)initWithCoder:(NSCoder *)aDecoder 
{
    if(self = [super initWithCoder:aDecoder]) {
        self.instanceVariable = [aDecoder decodeObjectForKey:INSTANCEVARIABLE_KEY];

       // similarly for other instance variables
       ....
}
    return self;
}

您可以以标准方式初始化对象，即

CustomObject *customObject = [[CustomObject alloc] init];

取自此答案的示例

Answer 2

您可以通过以下方式使用它：

.h 文件

@interface Score : NSObject {
    NSString *Username;
    NSString *TotalPoints;
    NSString *LifeRemains;
    NSString *ScoreDate;
}

@property (nonatomic, retain) NSString *Username;
@property (nonatomic, retain) NSString *TotalPoints;
@property (nonatomic, retain) NSString *LifeRemains;
@property (nonatomic, retain) NSString *ScoreDate;

在 .m 文件中

@synthesize Username, TotalPoints, LifeRemains, ScoreDate;

- (void)encodeWithCoder:(NSCoder *)encoder
{
//Encode properties, other class variables, etc
[encoder encodeObject:self.Username forKey:kScoreUsername];
[encoder encodeObject:self.TotalPoints forKey:kScoreTotalPoints];
[encoder encodeObject:self.LifeRemains forKey:kScoreLifeRemains];
[encoder encodeObject:self.ScoreDate forKey:kScoreDate];
}

- (id)initWithCoder:(NSCoder *)decoder
{
self = [super init];
if( self != nil )
{
    //decode properties, other class vars
    self.Username = [decoder decodeObjectForKey:kScoreUsername];
    self.TotalPoints = [decoder decodeObjectForKey:kScoreTotalPoints];
    self.LifeRemains = [decoder decodeObjectForKey:kScoreLifeRemains];
    self.ScoreDate = [decoder decodeObjectForKey:kScoreDate];
}
return self;
}

快乐的编码...