#define a global preprocessor directive in a separate file in Objective-C

Question

I want to define a global preprocessor directive in my app. For example:

In MyProgram.h, I define:

#define USE_LOCALHOST

I import this file from beginning in appDelegate.m.

For the later use, in another file, I refer to this global preprocessor directive.

In MyWebService.h, I define:

#ifdef USE_LOCALHOST
static NSString *MY_SERVER = @"http://192.168.1.130:8888";
#else
static NSString *MY_SERVER = @"http://myserver.com";
#endif

However, the value of MY_SERVER is always @"http://myserver.com". How to make it work properly? Thanks.

USE_LOCALHOST, USE_LOCAL_HOST?

tuledev
– tuledev

2015-09-09 08:40:30 +00:00
Commented Sep 9, 2015 at 8:40 — tuledev
– tuledev, Commented Sep 9, 2015 at 8:40
sorry, I just edited my post. Still the same question.

chipbk10
– chipbk10

2015-09-09 08:42:14 +00:00
Commented Sep 9, 2015 at 8:42 — chipbk10
– chipbk10, Commented Sep 9, 2015 at 8:42

Cy-4AH · Accepted Answer · 2015-09-09 09:23:44Z

3

Define it in .pch. And you will never forget to include .h-file where you have defined USE_LOCALHOST.

Or you can define it in build settings in Preprocessor Macros. For example only for Debug.

answered Sep 9, 2015 at 9:23

Cy-4AH

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1 Comment

chipbk10 Over a year ago

Thanks, it seems to be a good way to share the preprocessor directive among files.

WangYudong · Accepted Answer · 2015-09-09 08:58:06Z

2

#define works only in the file where it's defined in. But you can #import "MyProgram.h" in MyWebService.h and problem solved. Every time you need to access USE_LOCALHOST, just import the header file.

edited Sep 9, 2015 at 8:58

answered Sep 9, 2015 at 8:45

WangYudong

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3 Comments

chipbk10 Over a year ago

I already imported the "MyProgram.h" right from the beginning in AppDelegate.m.

WangYudong Over a year ago

Not AppDelegate.m, but try to import it in MyWebService.h

chipbk10 Over a year ago

Of course in that case, it will work. However, I don't want to do that. Each time, I need I have to give it a call to MyProgram.h. It's not the purpose of creating a global directive. Thanks to your response. Probably, my approach is wrong.

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