摘要： 【Working with nil】 It’s always a good idea to initialize scalar variables at the time you declare them, otherwise their initial values will contain garbage from the previous stack contents: This isn’t necessary for object pointers, because the compiler will automatically set the variable to nil ... 阅读全文

摘要： 【Determining Equality of Objects】 If you need to determine whether one object is the same as another object, it’s important to remember that you’re working with pointers.The standard C equality operator == is used to test equality between the values of two variables, like this: When dealing with... 阅读全文

摘要： 【NSLog中的%@】 There is one additional substitution token available in Objective-C, %@, used to denote an object. At runtime, this specifier will be substituted with the result of calling either the descriptionWithLocale: method (if it exists) or the description method on the provided object. The desc. 阅读全文