自定義對象要實現歸檔必須實現NSCoding協議

 NSCoding協議有兩個方法，encodeWithCoder方法對對象的屬性數據做編碼處理，initWithCoder解碼歸檔數據來初始化對象。

示例1

.h頭文件

 #import <Foundation/Foundation.h>
 @interface user : NSObject <NSCoding>
 @property(nonatomic,retain)NSString *name;
 @property(nonatomic,retain)NSString *email;
 @property(nonatomic,retain)NSString *pwd;
 @property(nonatomic,assign)int age;
 @end

.m實現文件

#import "user.h"
#define AGE @"age"
#define NAME @"name"
#define EMAIL @"email"
#define PASSWORD @"password"
@implementation user
//對屬性編碼
- (void)encodeWithCoder:(NSCoder *)aCoder
{
  [aCoder encodeInt:_age forKey:@"age"];
  [aCoder encodeObject:_name forKey:AGE];
  [aCoder encodeObject:_email forKey:EMAIL];
  [aCoder encodeObject:_pwd forKey:PASSWORD];
}
//對屬性解碼
- (id)initWithCoder:(NSCoder *)aDecoder
{
  self=[super init];
  if(self)
  {
    self.age=[aDecoderdecodeIntForKey:AGE];
    self.name=[aDecoderdecodeObjectForKey:NAME];
    self.email=[aDecoderdecodeObjectForKey:EMAIL];
    self.pwd=[aDecoderdecodeObjectForKey:PASSWORD];
  }
  return self;
}
-(void)dealloc
{
  [_name release];
  [_email release];
  [_pwd release];
  [super dealloc];
}
@end

main函數的調用

  user *userObj=[[user alloc] init];
  userObj.age=33;
  userObj.email=@"[email protected]";
  userObj.pwd=@"212212";
  userObj.name=@"ricard";
  NSString *path=[NSHomeDirectory() stringByAppendingPathComponent:@"Desktop/custom.text"];
  BOOL succ=[NSKeyedArchiver archiveRootObject:userObj toFile:path];
  if (succ) {
     NSLog(@"Hello, World!");
     user *usertemp=[NSKeyedUnarchiver unarchiveObjectWithFile:path];
  }

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