本文转载至 http://my.oschina.net/sunqichao/blog?disp=2&catalog=0&sort=time&p=3 这往往是引用的问题.ARC要求完整的前向引用,也就是说在MRC时代可能只需要在.h中申明@class就可以,但是在ARC中如果调用某个子类中未覆盖的父类中的方法的话,必须对父类.h引用,否则无法编译. 有一篇文章讲的很详细 本文部分实例取自iOS 5 Toturail一书中关于ARC的教程和公开内容,仅用于技术交流和讨论.请不要将本文的…

获取对象类型 type(object) >>> test_data = [1, 2, 3] >>> type(test_data) <type 'list'> >>> 判断对象是否是已知类型 isinstance(object, class-or-type-or-tuple) >>> test_data = 123 >>> isinstance(test_data, (int, str)) True…

>>> a=520 >>> type(a) <class 'int'> >>> a=' >>> type(a) <class 'str'> >>> a=5.2 >>> type(a) <class 'float'> >>> a=True >>> type(a) <class 'bool'> >>>…

class Foo(object): pass class Bar(Foo): pass obj = Bar() # isinstance用于判断,对象是否是指定类或其派生类的实例 print(isinstance(obj,Foo)) #True print(isinstance(obj,Bar))#True #精确的判断对象是否是指定类的实例 print(type(obj) == Bar) #True print(type(obj) == Foo) #False…

转自:http://stackoverflow.com/questions/8815200/receiver-type-for-instance-message-is-a-forward-declaration You're -init'ing an object without +alloc'ing it. That won't work You're declaring an object as a non-pointer type, that won't work either You'r…

错误原因:没有引入相关的头文件 http://stackoverflow.com/questions/8815200/receiver-type-for-instance-message-is-a-forward-declaration…

1. System.Object        The runtime requires every type to ultimately be derived from the System.Object type.        Because all types are ultimately derived from System.Object, you are guaranteed that every object of every type has a minimum set of…

1.All Types Are Derived from System.Object The CLR requires all objects to be created using the new operator(Employee e = new Employee("ConstructorParam1");) the new operator does: 1.It calculates the number of bytes required 2.It allocates memo…

项目中常用到工厂模式,工厂模式可以把创建对象的具体细节封装到Create函数中,减少重复代码,增强可读和可维护性.传统的工厂实现如下: class Widget { public: virtual int Init() { printf("Widget Init"); ; } }; class WidgetA : public Widget { public: virtual int Init() { printf("WidgetA Init"); ; } }; c…

写在前面 AutoMapper目录: [AutoMapper官方文档]DTO与Domin Model相互转换(上) [AutoMapper官方文档]DTO与Domin Model相互转换(中) [AutoMapper官方文档]DTO与Domin Model相互转换(下) 未完待续... 本篇目录: Custom Type Converters-自定义类型转换器 Custom Value Resolvers-自定义值解析器 Null Substitution-空值替换 Containers-IoC…