How to determine whether code is running in DEBUG / RELEASE build?

Check your project's build settings under 'Apple LLVM - Preprocessing', 'Preprocessor Macros' for debug to ensure that DEBUG is being set - do this by selecting the project and clicking on the build settings tab. Search for DEBUG and look to see if indeed DEBUG is being set.

Pay attention though. You may see DEBUG changed to another variable name such as DEBUG_MODE.

https://i.stack.imgur.com/LgTyF.png

then conditionally code for DEBUG in your source files

#ifdef DEBUG

// Something to log your sensitive data here

#else

// 

#endif

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For a solution in Swift please refer to this thread on SO.

Basically the solution in Swift would look like this:

#if DEBUG
    println("I'm running in DEBUG mode")
#else
    println("I'm running in a non-DEBUG mode")
#endif

Additionally you will need to set the DEBUG symbol in Swift Compiler - Custom Flags section for the Other Swift Flags key via a -D DEBUG entry. See the following screenshot for an example:

https://i.stack.imgur.com/rLan3.png

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Apple already includes a DEBUG flag in debug builds, so you don't need to define your own.

You might also want to consider just redefining NSLog to a null operation when not in DEBUG mode, that way your code will be more portable and you can just use regular NSLog statements:

//put this in prefix.pch

#ifndef DEBUG
#undef NSLog
#define NSLog(args, ...)
#endif

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Most answers said that how to set #ifdef DEBUG and none of them saying how to determinate debug/release build.

My opinion:

Edit scheme -> run -> build configuration :choose debug / release . It can control the simulator and your test iPhone's code status. Edit scheme -> archive -> build configuration :choose debug / release . It can control the test package app and App Store app 's code status.

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Swift and Xcode 10+

#if DEBUG will pass in ANY development/ad-hoc build, device or simulator. It's only false for App Store and TestFlight builds.

Example:

#if DEBUG
   print("Not App Store or TestFlight build")
#else
   print("App Store or TestFlight build")
#endif

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zitao xiong's answer is pretty close to what I use; I also include the file name (by stripping off the path of FILE).

#ifdef DEBUG
    #define NSLogDebug(format, ...) \
    NSLog(@"<%s:%d> %s, " format, \
    strrchr("/" __FILE__, '/') + 1, __LINE__, __PRETTY_FUNCTION__, ## __VA_ARGS__)
#else
    #define NSLogDebug(format, ...)
#endif

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In xcode 7, there is a field under Apple LLVM 7.0 - preprocessing, which called "Preprocessors Macros Not Used In Precompiled..." I put DEBUG in front of Debug and it works for me by using below code:

#ifdef DEBUG
    NSString* const kURL = @"http://debug.com";
#else
    NSString* const kURL = @"http://release.com";
#endif

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Just one more idea to detect:

DebugMode.h

#import <Foundation/Foundation.h>

@interface DebugMode: NSObject
    +(BOOL) isDebug;
@end

DebugMode.m

#import "DebugMode.h"

@implementation DebugMode
+(BOOL) isDebug {
#ifdef DEBUG
    return true;
#else
    return false;
#endif
}
@end

add into header bridge file:

#include "DebugMode.h"

usage:

DebugMode.isDebug()

It is not needed to write something inside project properties swift flags.

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Adding this for people working with Kotlin multiplatform ios debug mode. Here is how you can determine if the build is debug or release.

if (Platform.isDebugBinary) {
     NSLog(message ?: "", "")
}

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Not sure if I answered you question, maybe you could try these code:

#ifdef DEBUG
#define DLOG(xx, ...)  NSLog( \
    @"%s(%d): " \
    xx, __PRETTY_FUNCTION__, __LINE__, ##__VA_ARGS__ \  
    )
#else
#define DLOG(xx, ...)  ((void)0)
#endif 

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