iOS技术文档No.12 AppKit_NScoder

NSCoding是一个protocol. 如果实现了NSCoding，需要实现其中的两个方法:

- (void)encodeWithCoder:(NSCoder *)aCoder;
- (id)initWithCoder:(NSCoder *)aDecoder; // NS_DESIGNATED_INITIALIZER

方法中的主要的参数就是NSCoder,它是archivie字节流的抽象类.可以将数据写入一个coder,也可以从coder中读取我们写入的数据. NSCoder是一个抽象类,不能直接使用它来创建对象. 但是可以通过其子类NSKeyedUnarchiver从字节流中读取数据,NSKeyedArchiver将对象写入到字节流。本文以书籍为例:

新建一个Book类，Book.h中的代码:

#import <Foundation/Foundation.h>
#import <UIKit/UIKit.h>
 
@interface Book : NSObject<NSCoding>
 
@property (strong,nonatomic) UIImage *ConverPicture;
 
@property (strong,nonatomic) NSString *BookName;
 
@property (strong,nonatomic) NSString *Author;
 
@property (strong,nonatomic) NSNumber *Price;
 
@end

Book.m中实现NSCoding的两个方法，注意中UIImage的写法与其他有所不同:

@implementation Book
 
- (void)encodeWithCoder:(NSCoder *)aCoder{
     
    //注意这里是存储的是JPG图片的调用
    [aCoder encodeObject:UIImageJPEGRepresentation(self.ConverPicture,1.0)forKey:@"ConverPicture"];
    [aCoder encodeObject:_BookName forKey:@"BookName"];
    [aCoder encodeObject:_Author forKey:@"Author"];
    [aCoder encodeObject:_Price forKey:@"Price"];
     
}
 
- (id)initWithCoder:(NSCoder *)aDecoder{
     
    self.ConverPicture=[UIImage imageWithData:[aDecoder decodeObjectForKey:@"ConverPicture"]];
    self.BookName=[aDecoder decodeObjectForKey:@"BookName"];
    self.Author=[aDecoder decodeObjectForKey:@"Author"];
    self.Price=[aDecoder decodeObjectForKey:@"Price"];
    return self;
     
}
@end