Foundation框架的归档功能
将对象存储转换为二进制序列的过程成为归档、打包或编码，逆变换称为解档、解码或对象还原。
可以使用NSKeyedArchiver和NSKeyedUnarchiver完成对象的归档和解档操作，而他们都是抽象类NSCoder的子类。
所有可以归档的对象都必须要适用于协议NSCoding。协议NSCoding在Foundation/NSObject.h中定义，NSObject自身并不采用该协议。NSString、NSDictionary等Foundation框架的主要类都适用协议NSCoding。
协议NSCoding按照如下方式声明:
@protocolNSCoding
-(void)encodeWithCoder:(NSCoder*)coder
-(id)initWithCoder:(NSCoder*)coder
归档方法的定义
协议NSCoding中，函数encodeWithCoder：定义了归档自身的方法。
- (void)encodeWithCoder:(NSCoder *)coder
{
[super encodeWithCoder:coder];
//超类需要适用NSCoding协议
[coder encodeObject:对象 forKey:关键词字符串];
[coder encodeInt:实数变量 forKey:关键词字符串];
}
如果超类不适用协议NSCoding，则不能调用encodeWithCoder：方法。
类自身对包含的实例变量归档。在类没有自己的实例变量且超类中定义了方法encodeWithCoder：的情况下，该方法就不需要在定义了。
通过使用NSString字符串作为键值，可以指定归档解档的内容。让某个类实例归档时，它的实例变量必须指定成不同的键值。在单个对象内部，如果超类使用了一个键值，那么子类中就不能使用该键值。键值只需在同一个类内区分出来即可，不同的类可使用相同的键值。
当对象图有闭环时，同一个对象会重复要求归档，实际上已归档的对象是不用重复归档的。
解档方法的定义
- (instancetype)initWithCoder:(NSCoder *)coder{
self= [superinitWithCoder:coder];
//超类不适应于协议NSCoding时，
//建议使用 self = [super init];
if (self) {
self.name= [coder decodeObjectForKey: 键值];
self.age= [coder decodeIntForKey: 键值];
}
returnself;
}
归档示例程序:
main.m
#import <Foundation/Foundation.h>
#import"Person.h"
int main(intargc,constchar* argv[]) {
@autoreleasepool {
Person * p = [[Person alloc] init];
p.name= @"lu";
p.age=18;
p.weight=100.0;
BOOLisSuccess = [NSKeyedArchiver archiveRootObject:p toFile:@"/Users/lu/Desktop/test.plist"];if(isSuccess) {NSLog(@"归档成功");
}else{
NSLog(@"归档失败");
}
}
return0;
}
解档示例程序：
main.m
intmain(intargc,constchar* argv[]) {
@autoreleasepool {
//解档
Person * p = [NSKeyedUnarchiver unarchiveObjectWithFile:@"/Users/lu/Desktop/test.plist"];
NSLog(@"%@",p.name);
NSLog(@"%d",p.age);
NSLog(@"%f",p.weight);
}
return0;
}
若类中实例变量为其他类对象，则还需要在其他类中实现encodeWithCoder：和initWithCoder：方法。
示例程序:
Dog.m
#import"Dog.h"
@implementation Dog
- (void)encodeWithCoder:(NSCoder *)coder{
[coder encodeObject:self.nameforKey:@"name"];
[coder encodeInt:self.ageforKey:@"age"];}
- (instancetype)initWithCoder:(NSCoder *)coder{
self= [superinit];
if (self) {
self.name= [coder decodeObjectForKey:@"name"];self.age= [coder decodeIntForKey:@"age"]; }
return self;
}
@end
student.m
#import"Student.h"
#import"Dog.h"
@implementationStudent
//归档
- (void)encodeWithCoder:(NSCoder *)coder{
[coder encodeObject:self.nameforKey:@"name"];
[coder encodeInt:self.scoreforKey:@"score"];
[coder encodeInt:self.numberforKey:@"number"];
[coder encodeObject:self.dogforKey:@"dog"];}
//解档
- (instancetype)initWithCoder:(NSCoder *)coder{
self = [superinit];
if (self) {
self.name= [coder decodeObjectForKey:@"name"];
self.score= [coder decodeIntForKey:@"score"];
self.number= [coder decodeIntForKey:@"number"];
self.dog= [coder decodeObjectForKey:@"dog"];
}
return self;
}
@end
main.m
int main(intargc,constchar* argv[]) {
@autoreleasepool {
Student * stu = [[Student alloc] init];
stu.name= @"di";
stu.score=70;
stu.number=20;
Dog * d = [[Dog alloc] init];
d.name= @"Chen";
d.age=10;
stu.dog= d;
//归档
BOOL isSuccess = [NSKeyedArchiver archiveRootObject:stu toFile:@"/Users/lu/Desktop/Stu.txt"];if(isSuccess) {NSLog(@"Yes");
}else{
NSLog(@"NO");
}
//解档
Student * stu3 = [NSKeyedUnarchiver unarchiveObjectWithFile:@"/Users/lu/Desktop/Stu.txt"];NSLog(@"%@", stu3.name);
NSLog(@"%d", stu3.score);
NSLog(@"%d", stu3.number);
NSLog(@"%@", stu3.dog.name);
NSLog(@"%d", stu3.dog.age);
}
return0;
}
对多个对象进行归档，可以先将多个对象存储于NSArray、NSMutableArray、NSDictionary或NSMutableDictionary中，再进行归档。
示例程序：
NSArray* stuArray = @[stu, stu1, stu2];
BOOLisSuccess = [NSKeyedArchiver archiveRootObject:stuArray toFile:@"/Users/lu/Desktop/stuArray.txt"];
if(isSuccess) {
NSLog(@"Yes");
}else{
NSLog(@"NO");
}
最后一种方式利用NSData对多个对象进行归档解档
示例程序
main.m
#import
#import"Person.h"
int main(intargc,constchar* argv[]) {
@autoreleasepool {
Person * p = [[Person alloc] init];
p.name= @"dou";
p.age=22;
p.weight=120.00;
Person * p2 = [[Person alloc] init];
p2.name= @"dashu";
p2.age=24;
p2.weight=140.3;
NSMutableData * data = [NSMutableData data];// 根据二进制流创建NSkeyedArchiver对象
NSKeyedArchiver * archiver = [[NSKeyedArchiver alloc] initForWritingWithMutableData:data];
// 对对象进行归档操作
[archiver encodeObject:p forKey:@"person1"];
[archiver encodeObject:p2 forKey:@"person2"];
// 结束归档
/*** -[NSKeyedArchiver dealloc]: warning: NSKeyedArchiver deallocated without having had -finishEncoding called on it.
归档如果没有结束 finishEncoding就不会归档成功，产生文件无法打开 The data couldn't be read because it isn't in the correct format.
*/
[archiver finishEncoding];
BOOL isSuccess = [data writeToFile:@"/Users/lu/Desktop/Data.plist"atomically:YES];if(isSuccess) {
NSLog(@"归档成功！");
}else{
NSLog(@"归档失败");
}
//解档NSData * data = [NSData dataWithContentsOfFile:@"/Users/lu/Desktop/Data.plist"]; NSKeyedUnarchiver * unarchiver = [[NSKeyedUnarchiver alloc] initForReadingWithData:data];
Person * p = [unarchiver decodeObjectForKey:@"person1"];
Person * p2 = [unarchiver decodeObjectForKey:@"person2"];
//结束解档 解档没有finishDecoding无影响
// [unarchiver finishDecoding];
NSLog(@"%@", p.name);
NSLog(@"%d", p.age);NSLog(@"%f", p.weight);
NSLog(@"%@", p2.name);NSLog(@"%d", p2.age);NSLog(@"%f", p2.weight);
}
return0;
}
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