请问什么是便利构造器（快速构造器）

类似于Java中的构造方法,
指的是在init的时候,同时给属性变量赋值的方法

比如
@interface Person : NSObject{
    int _age;
    NSString *_name;
}
- (Person *)initWithAge: (int)age andWithName: (NSString *)name; 
+ (Person *)initWithAge: (int)age andWithName: (NSString *)name;//这个类方法在返回Person对象时,就可以给_age和_name赋值,这个就是便利构造器
@end

@implementation Person
- (Person *)initWithAge: (int)age andWithName: (NSString *)name{
    _age = age;
    _name = name;
}
+ (Person *)initWithAge: (int)age andWithName: (NSString *)name
{
    return [[Person alloc] initWithAge:age andWithName:name];
}
@end


int main()
{
    Person *p  = [Person initWithAge: 10 andWithName: @"jason"];// 在init时就赋值了age和name属性

    return 0;
}