designated initializers

#import <Foundation/Foundation.h>

@interface Profile : NSObject

@property (nonatomic, copy) NSString *name;

- (instancetype)init;

- (instancetype)initWithName:(NSString *)name NS_DESIGNATED_INITIALIZER;

@end

#import "Profile.h"

@implementation Profile

- (instancetype)init {
    // 必须调用指定构造器
    return [self initWithName:@"Unknown"];
}

- (instancetype)initWithName:(NSString *)name {
    // 必须调用父类的指定构造器
    self = [super init];
    if (self) {
        _name = [name copy];
    }
    return self;
}

@end