如何将类中存在的 NSMutablearray 保存到文件中？

Question

学生.h

#import <Foundation/Foundation.h>
#import "Subject.h"

@interface Student : NSObject <NSCoding> {
    NSString *studentID;
    NSString *studentName;
    NSMutableArray<Subject* > *subjects;
}

@property (copy) NSString *studentID;
@property (copy) NSString *studentName;
@property (copy) NSMutableArray<Subject* > *subjects;

-(Student *)initWithStudentID:(NSString *)ID andStudentName:(NSString *)name;

-(void)addSubject:(Subject *) subject;
@end

学生.m

#import "Student.h"

@implementation Student

@synthesize  studentName;
@synthesize  studentID;
@synthesize  subjects;

-(Student *)initWithStudentID:(NSString *)ID andStudentName:(NSString *)name {

    Student *student = [[Student alloc] init];

    student.studentID = [NSString stringWithString:ID];
    student.studentName = [NSString stringWithString:name];

    return student;
}

-(void)addSubject:(Subject *)subject{
    if(subjects==nil){
        subjects=[[NSMutableArray alloc]init];
    }
    [subjects addObject:subject];


}

- (id)initWithCoder:(NSCoder *)aDecoder {
    if (self = [super init]) {
        [self setStudentID:[aDecoder decodeObjectForKey:@"studentID"]];
        [self setStudentName:[aDecoder decodeObjectForKey:@"studentName"]];
        [[NSUserDefaults standardUserDefaults] setObject:[NSKeyedArchiver archivedDataWithRootObject:subjects] forKey:@"subjects"];
           }
    return self;
}

- (void)encodeWithCoder:(NSCoder *)aCoder {
    [aCoder encodeObject:studentID forKey:@"studentID"];
    [aCoder encodeObject:studentName forKey:@"studentName"];
    [aCoder encodeObject:subjects forKey:@"subjects"];
}

@end

主题.h

#import <Foundation/Foundation.h>

@interface Subject : NSObject
@property  NSString *subjectID;
@property  NSString *subjectName;
@end

主题.m

#import "Subject.h"

@implementation Subject
@end

Main.m

#import <Foundation/Foundation.h>
#import "Student.h"

int main(int argc, const char * argv[]) {
    @autoreleasepool {
        Student *student1=[[Student alloc ]initWithStudentID:@"Nirmal" andStudentName:@"101"];

        Subject *subject = [Subject alloc];
        subject.subjectID=@"S01";
        subject.subjectName=@"PHY";

        [student1 addSubject:subject];

        [NSKeyedArchiver archiveRootObject:student1 toFile:@"/Users/kuzhandaivel/Documents/nirmal.plist"];

        Student *student2=[NSKeyedUnarchiver unarchiveObjectWithFile:@"/Users/kuzhandaivel/Documents/nirmal.plist"];

        NSLog(@"%@",student2.studentID);
        NSLog(@"%@",student2.studentName);
        NSLog(@"%@",[student2.subjects description]);

    }
    return 0;
}

如何将类中存在的 NSMutablearray 保存到文件中？ 上面的程序在以下行抛出以下错误：

[aCoder encodeObject:subjects forKey:@"subjects"];

encodeWithCoder 函数存在于 student.m 文件中。

Archiver[4667:102276] -[Subject encodeWithCoder:]：无法识别的选择器发送到实例 0x1006000a0 2016-10-22 20:25:57.738 Archiver[4667:102276] *** 由于未捕获的异常“NSInvalidArgumentException”而终止应用程序，原因：“-[Subject encodeWithCoder:]：无法识别的选择器发送到实例 0x1006000a0” *** 首先抛出调用堆栈：

Answer 1

Subject 也需要像Student 一样符合NSCoding 协议。

您要归档的根对象中存储的每个类都必须符合NSCoding 协议。

Answer 2

对象层次结构中的所有对象都需要确认 NSCoding 协议才能保存到存档。

如果你看到 NSString 类

@interface NSString : NSObject <NSCopying, NSMutableCopying,NSSecureCoding>

它实现了 NSSecureCoding，它是 NSCoding 的子类。所以需要对所有的子对象和子对象的子对象等实现NSCoding协议。 它基本上遍历所有子对象并一一编码。因此，如果您没有在其中任何一个上实施，它将失败。

Archiver[4667:102276] -[Subject encodeWithCoder:]：无法识别 选择器发送到实例 0x1006000a0 2016-10-22 20:25:57.738 Archiver[4667:102276] * 由于未捕获的异常而终止应用程序 'NSInvalidArgumentException'，原因：'-[Subject encodeWithCoder:]： 无法识别的选择器发送到实例 0x1006000a0' * 首先抛出调用栈：

我认为这句话说明了一切。

[主题 encodeWithCoder:(NSCoder *)aCoder]