数据存储，model 对象归档本地化

• (IBAction)saveBtnOnclick:(UIButton *)sender {
  Student *student=[[Student alloc]init];
  student.name=@"bp";
  student.age=25;
  student.height=1.9;
  student.weight=62;

  //获取文件路径
  NSString *docPath=[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
  NSString *path=[docPath stringByAppendingPathComponent:@"student.bp"];

  //将自定义的对象保存到文件
  [NSKeyedArchiver archiveRootObject:student toFile:path];
  }

• (IBAction)readBtnOnclick:(UIButton *)sender {
  NSString *docPath=[NSSearchPathForDirectoriesInDomains(NSDocumentDirectory, NSUserDomainMask, YES) lastObject];
  NSString *path=[docPath stringByAppendingPathComponent:@"student.bp"];

  //从文件中读取对象
  Student *student=[NSKeyedUnarchiver unarchiveObjectWithFile:path];
  NSLog(@"%@ %D %.1f %f",student.name,student.age,student.height,student.weight);
  }

-(void)encodeWithCoder:(NSCoder *)aCoder
{
[aCoder encodeObject:self.name forKey:@"name"];
[aCoder encodeInteger:self.age forKey:@"age"];
[aCoder encodeDouble:self.height forKey:@"height"];
[aCoder encodeFloat:self.weight forKey:@"weight"];
}
-(id)initWithCoder:(NSCoder *)aDecoder
{
if (self=[super init]) {
self.name=[aDecoder decodeObjectForKey:@"name"];
self.age=[aDecoder decodeIntegerForKey:@"age"];
self.height=[aDecoder decodeDoubleForKey:@"height"];
self.weight=[aDecoder decodeFloatForKey:@"weight"];
}
return self;
}