How to find unused ivars in Xcode

Question

Sometimes I declare an ivar but after a while I am no longer using it. I would like to remove this sort of cruft from my code, but I cannot find a warning that will show me my unused ivars.

Is there a tool or built in feature of Xcode that will allow me to find all of my unused ivars?

I see that the static analyzer has CLANG_ANALYZER_OBJC_UNUSED_IVARS, but it does not seem to do anything.

@implementation AppDelegate
{
@private
    BOOL _foo; // Never read or written to
}

Runing the analyzer in Xcode 5 with CLANG_ANALYZER_OBJC_UNUSED_IVARS (unused ivars) set to YES never produces a warning.

Veator

Delete (or comment out) the ivar, compile, and see if there are any complaints. – Lifegiving

Yep that would work, but for a large project that is tedious, and I was hoping for an automated tool that look through all classes without me having to modify code. – Veator

The other option is to not add so dang many ivars in the first place. – Lifegiving

Answer 1

Based on the relevant Clang source code and a couple of quick tests, it seems that the analyzer does not look at ivars that are not both declared in the @interface and marked @private.

@interface Igloo : NSObject
{
    NSString * address;    // No warning
    @private
    NSInteger radius;    // Warning
}
@end

@implementation Igloo
{
    NSInteger numWindows;    // No warning
    @private    // Has no real effect, of course; just testing
    NSString * doormatText;    // No warning
}

@end

I suggest filing a bug/submitting a patch.

Henke

are you saying analyzer only look at ivars are both declared in the @interface and marked @private? double not confused me.. – Perri

Right, @BryanChen, what you said. BOOL analyzed = (declaredInInterface && markedPrivate); – Henke

Seems odd, putting iVars in the @interface seems to be a deprecated pattern. – Meatman

Answer 2

In Xcode from product menu click on analyze... It will show you unused variables. This will also tell you about dead code.

Tuberculosis

Analyze definitely needs more awareness – Oestriol

Answer 3

It appears that the static analyzer option only works if you declare the ivar in the header file.

This generates the analyzer warning correctly:

// AppDelegate.h
@interface AppDelegate : NSObject <UIApplicationDelegate>
{
    BOOL _foo; // never read or written
}
@end

Neither of these generates any sort of analyzer warning:

//  AppDelegate.m
@interface AppDelegate ()
{
@private
    BOOL _goo; // never read or written
}
@end

@implementation AppDelegate
{
@private
    BOOL _hoo; // never read or written
}
@end

So it looks like you cannot use the modern syntax to keep ivars in the .m file if you want to check for unused ivars.

Veator