可重用的 NSMutableDictionary
该论坛中的某人向我提出了一个效果很好的代码解决方案，但根据我的理解，我想知道这两个代码块之间有什么区别：
块 1
NSMutableDictionary* step_info = [NSMutableDictionary dictionary];
块 2
NSMutableDictionary* step_info = nil;
step_info = [NSMutableDictionary dictionary];
可能还需要提到的是，step_info 必须被填充并重复使用以加载到另一个 NSmutabledictionary 中。
感谢您的帮助
Someone in that forum proposed me a code solution that worked great, but for my understanding, I would like to know what is the difference between the 2 blocks of code:
Block 1
NSMutableDictionary* step_info = [NSMutableDictionary dictionary];
Block 2
NSMutableDictionary* step_info = nil;
step_info = [NSMutableDictionary dictionary];
It is may be also important to mention that step_info has to be filled and reuse repeatedly to load into another NSmutabledictionary.
Thank's for your help
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没有任何。编译器会优化
step_info = nil并留下完全相同的代码。以下是您可以采取的另一种方法：
None. The compiler optimises
step_info = nilaway and you're left with the exact same code.The following is another approach you could take:
首先使用
NSMutableDictionary* step_info;可以让您稍后在同一代码块中使用step_info = [NSMutableDictionary Dictionary]。如果您希望在多个方法中为step_info赋值，最好在头文件的
@interface部分添加NSMutableDictionary* step_info。这样，您就可以在实现文件中的任何方法中使用step_info = [[NSMutableDictionary alloc] init]，然后按以下方式分配值和键：
[step_info setValue: value forKey: key];Having
NSMutableDictionary* step_info;first allows you to usestep_info = [NSMutableDictionary dictionary]later in the same block of code.If you wish to assign a value to step_info in multiple methods, it'd be better if you add
NSMutableDictionary* step_infoin the@interfacesection of the header file.That way you can use
step_info = [[NSMutableDictionary alloc] init]in any method in your implementation file, then assign values and keys this way:[step_info setValue: value forKey: key];