StackOverflow2013

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copied!<p>You have to use a .h file, just like with .m files, to declare what you're doing in another file. So, you need something like this for this scenario (these are incomplete):</p> <p><strong>returnfloat.c</strong></p> <pre><code>float returnFloat() { return 10.0; } </code></pre> <p><strong>returnfloat.h</strong></p> <pre><code>float returnFloat(void); </code></pre> <p><strong>usefloat.m</strong></p> <pre><code>#import "returnfloat.h" - (void) someMethod { float ten = returnFloat(); } </code></pre> <p>The problem (given away by your "implicit declaration" warnings) is that the compiler is assuming that you are calling something that returns an <code>int</code> or <code>id</code>, not a <code>float</code>. When you work with C, things need to be prototyped (GCC will treat the .c file like C, and all C rules apply, even though you're in an Objective-C project).</p> <hr> <p>If you'd like to see an example, here's something from one of my projects -- production code (you can write pure C in a file ending in .m, and GCC will treat it like Objective-C in some ways):</p> <p><strong>DebugF.m</strong></p> <pre><code>#import "DebugF.h" void __Debug(const char *file, int line, NSString *format, ...) { #ifdef DEBUG /* Wraps NSLog() with printf() style semantics */ #endif } </code></pre> <p><strong>DebugF.h</strong></p> <pre><code>#ifndef __DEBUGF_H_INCLUDED__ #define __DEBUGF_H_INCLUDED__ #ifdef DEBUG #define DebugF(args...) __Debug(__FILE__, __LINE__, args) #else #define DebugF(...) #endif /* DEBUG */ void __Debug(const char *file, int line, NSString *fmt, ...); #endif /* __DEBUGF_H_INCLUDED */ </code></pre> <p><strong>SomeViewController.m</strong></p> <pre><code>DebugF(@"Got these arguments: %u, %@, %@", 4, anObject, [anObject somethingElse]); </code></pre>

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