归档学习记录

归档和Java中得序列化机制类似，都是将对象以某个格式保存在制定文件中，方便以后再从文件中恢复它们。

Foundation中常用的类如NSDictionary均实现了NSCoding方法，可以直接序列化

自定义的OC对象需要实现NSCoding协议，并实现其中的两个方法：

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

看例子：

Student.h:

#import <Foundation/Foundation.h>@interface Student : NSObject  <NSCoding>@property (nonatomic, copy) NSString *name;@property (nonatomic, assign) int age;- (id)initWithName: (NSString *) name andAge: (int) age;+ (id)studentWithName: (NSString *)name andAge: (int) age;@end

Student.m

#import "Student.h"@implementation Student- (id)initWithName:(NSString *)name andAge:(int)age {    if (self = [super init]) {        self.name = name;        self.age = age;    }        return self;}+ (id)studentWithName:(NSString *)name andAge:(int)age {    Student *student = [[Student alloc] initWithName:name andAge:age];    return student;}#pragma mark 归档- (void)encodeWithCoder:(NSCoder *)aCoder {    // 调用NSCoder的方法归档对象的每一个变量    [aCoder encodeObject:_name forKey: @"name"];    [aCoder encodeInteger:_age forKey: @"age"];}#pragma mark 从归档中恢复对象-(id)initWithCoder:(NSCoder *)aDecoder {    NSString *name = [aDecoder decodeObjectForKey: @"name"];    int age = [aDecoder decodeIntegerForKey: @"age"];        return [Student studentWithName:name andAge:age];}-(NSString *)description {    return [NSString stringWithFormat:@"name = %@, age = %i", _name, _age];}@end

main.m

#import <Foundation/Foundation.h>#import "Student.h"#pragma mark 归档系统已经实现NSCoding协议的对象（如NSDictionary）void archiver() {    NSDictionary *dict = [NSDictionary dictionaryWithObjectsAndKeys:@"v1", @"k1", @"v2", @"k2", @"v3", @"k3", nil];    [NSKeyedArchiver archiveRootObject:dict toFile: @"/Users/zzqiltw/Desktop/dict.archiver"];// 打开文件后是乱码        NSDictionary *dict2 = [NSKeyedUnarchiver unarchiveObjectWithFile:@"/Users/zzqiltw/Desktop/dict.archiver"];    [dict2 enumerateKeysAndObjectsUsingBlock:^(id key, id obj, BOOL *stop) {        NSLog(@"%@ -> %@", key, obj);    }];}#pragma mark 归档自定义的已经实现NSCoding协议的对象Studentvoid archiver2() {    Student *student = [Student studentWithName:@"zzq" andAge:22];    [NSKeyedArchiver archiveRootObject:student toFile:@"/Users/zzqiltw/Desktop/student.archiver"];        Student *student2 = [NSKeyedUnarchiver unarchiveObjectWithFile:@"/Users/zzqiltw/Desktop/student.archiver"];        NSLog(@"student2: %@", student2);}#pragma mark 多对象归档void archiver3() {    Student *student = [Student studentWithName:@"zzq" andAge:22];    NSDictionary *dict = [NSDictionary dictionaryWithObjectsAndKeys:@"v1", @"k1", @"v2", @"k2", @"v3", @"k3", nil];    // 创建一个NSMutableData用来保存归档数据，多个对象归档完data写入文件    NSMutableData *data = [NSMutableData data];    NSKeyedArchiver *archiver = [[NSKeyedArchiver alloc] initForWritingWithMutableData:data];        [archiver encodeObject:dict forKey:@"myDict"];    [archiver encodeObject:student forKey:@"aStudent"];    [archiver encodeInteger:10 forKey:@"int"];    [archiver finishEncoding];        if ([data writeToFile:@"/Users/zzqiltw/Desktop/Objects.archiver" atomically:YES] == NO) {        NSLog(@"归档失败");    } else {        NSLog(@"归档成功");    }        NSMutableData *newData = [NSMutableData dataWithContentsOfFile:@"/Users/zzqiltw/Desktop/Objects.archiver"];    NSKeyedUnarchiver *unarchiver = [[NSKeyedUnarchiver alloc] initForReadingWithData:newData];    Student *newStudent = [unarchiver decodeObjectForKey:@"aStudent"];    NSInteger a = [unarchiver decodeIntegerForKey:@"int"];    NSDictionary *newDict = [unarchiver decodeObjectForKey:@"myDict"];        NSLog(@"%@", newStudent);    NSLog(@"%@", newDict);    NSLog(@"%zi", a);        }int main(int argc, const char * argv[]){    @autoreleasepool {//        archiver();//        archiver2();        archiver3();    }    return 0;}