How to define a preprocessor symbol in Xcode

Steph_Thirion_36182 0
Viewed 106097

Is it possible to set a symbol for conditional compilation by setting up properties in an Xcode project?

My aim is to to create a symbol that is available to all files, without having to use import/include, so that a set of common classes can have a special behavior in some projects. Like the following, but with my own symbols.

#if TARGET_IPHONE_SIMULATOR
    ...
#endif
c-preprocessor xcode objective-c
8 Answers

Go to your Target or Project settings, click the Gear icon at the bottom left, and select "Add User-Defined Setting". The new setting name should be GCC_PREPROCESSOR_DEFINITIONS, and you can type your definitions in the right-hand field.

Per Steph's comments, the full syntax is:

constant_1=VALUE constant_2=VALUE

Note that you don't need the '='s if you just want to #define a symbol, rather than giving it a value (for #ifdef statements)

Ben_Gottlieb_66940

You don't need to create a user-defined setting. The built-in setting "Preprocessor Macros" works just fine. alt text http://idisk.mac.com/cdespinosa/Public/Picture%204.png

If you have multiple targets or projects that use the same prefix file, use Preprocessor Macros Not Used In Precompiled Headers instead, so differences in your macro definition don't trigger an unnecessary extra set of precompiled headers.

cdespinosa_259720

For Xcode 9.4.1 and C++ project. Adding const char* Preprocessor Macros to both Debug and Release builds.

  1. Select your project

    select project

  2. Select Build Settings

    select build settings

  3. Search "Preprocessor Macros"

    search1 search2

  4. Open interactive list

    open interactive list

  5. Add your macros and don't forget to escape quotation

    add path

  6. Use in source code as common const char*

    ...
#ifndef JSON_DEFINITIONS_FILE_PATH
static constexpr auto JSON_DEFINITIONS_FILE_PATH = "definitions.json";
#endif
...
FILE *pFileIn = fopen(JSON_DEFINITIONS_FILE_PATH, "r");
...
user_52169490
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