To comment out a chunk of code, you’d add /* in front and */ at the end. In the old days of C, the only form of commenting was /* … */. It’s used for different purposes, but it’s always a blunt instrument. Conditional compilation: Commenting out codeĬonditional compilation, in its various flavors ( #if, #ifdef, etc.), is a way to selectively enable or disable chunks of code. m file is then: NSString *const JMRResponseSuccess = 6. h file: extern NSString *const JMRResponseSuccess So we want to define a constant pointer.Ĭonstant strings are often shared across multiple files, so here’s how to declare the constant in the.

Only this time, we’re defining a constant string, which is really an object, which is expressed in Objective-C as a pointer. Constants: String constants Smell #define JMRResponseSuccess with numeric constants, use the language to define a constant. One of these is the ability to inline functions: static inline CGFloat width(UIView *view) AddressRow 5. (And even then, have your macro call another function and shift as much as you can to the function.)Īnd this isn’t your dad’s C! The C language continues to adopt small pieces of C++. Just because you’re in Objective-C doesn’t mean you can’t use plain C functions! Unless your custom macro relies on Xcode preprocessor macros like _LINE_, rewrite it as a standalone function. Use #import instead it eliminates the need for those #ifndef include guards. Unless you’re delivering platform-agnostic C or C++ code, there’s no reason to use #include, along with the accompanying include guards. Let’s start with a simple one that comes from our C heritage: Smell #include 'foo.h'

Conditional compilation: Supporting multiple projects or platforms.

Conditional compilation: Switching between staging and production URLs.

Conditional compilation: Switching between experiments.

Conditional compilation: Commenting out code.

Here are some common Xcode preprocessor macros, and how to replace them:

And for #define macros used as constants, there are certain pitfalls to avoid-when we could just avoid them altogether. …But I want to question pretty much everything else! Why does it matter? Because every time you use the preprocessor, what you see isn’t what you compile. For example, #import directives are vital. It examines source files from the current directory down, showing preprocessor macros use that you should double-check. Here’s a handy command to run from Terminal. This post is part of the Code Smells in Objective-C series. C++ programmers have had this beat into them: “Don’t use the preprocessor to do something the language itself provides.” Unfortunately, more than a few Objective-C programmers have yet to get that message. With few exceptions, using Xcode preprocessor macros is a code smell.

Use xcode for c programming