错误：使用#defined常量的预期表达式 [英] Error: expected expression on line using #defined constant

问题描述

我这样做

  if（[resourceCompletionReward objectAtIndex：experienceD]！= 0）{
  

但是Xcode给我一个错误：

预期表达式

我已将 experienceD p>

  #define experienceD 0; 
  

我做错了什么？

解决方案

分号不应该在那里。

  #define experience D 0 
 
 
 
 
这也是一个很好的做法。以这样的UPPER_CASE_NOTATION命名常量。
 
 
 
为了完整性，我将补充苹果的建议（从 Cocoa的编码指南）
 
 
一般来说，不要使用#define预处理器命令来创建常量。对于整数常量，使用枚举，对于浮点常量，使用const限定符
 
 
以及
 
 
如果常量与其他常量无关，可以使用const创建一个整数常量;否则，使用枚举
 
 
所以在你的具体情况下，最好将你的常量定义为
  static const int ExperienceD = 0; 
  
 
I'm doing this
if ([resourceCompletionReward objectAtIndex:experienceD] != 0) {
But Xcode is giving me an error:

  
Expected expression
I've defined experienceD as
#define experienceD 0;
What am I doing wrong?
解决方案
The semicolon shouldn't be there.
#define experienceD 0
will compile just fine.

Also it's a good practice to name constants with an UPPER_CASE_NOTATION like this.

For completeness I will add that Apple suggests (from the Coding Guidelines for Cocoa)

  
In general, don’t use the #define preprocessor command to create constants. For integer constants, use enumerations, and for floating point constants use the const qualifier
and also

  
You can use const to create an integer constant if the constant is unrelated to other constants; otherwise, use enumeration
So in your specific case it would be better to define your constant as
static const int ExperienceD = 0;


                        
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