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.

Delete (or comment out) the ivar, compile, and see if there are any complaints. — Hot Licks, Jan 14 '14 at 00:08
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. — Skotch, Jan 14 '14 at 00:11
The other option is to not add so dang many ivars in the first place. — Hot Licks, Jan 14 '14 at 00:12

score 4 · Accepted Answer · answered Jan 13 '14 at 23:25

4

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.

answered Jan 13 '14 at 23:25

jscs

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are you saying analyzer only look at ivars are both declared in the @interface and marked @private? double not confused me.. – Bryan Chen Jan 14 '14 at 00:02
Right, @BryanChen, what you said. `BOOL analyzed = (declaredInInterface && markedPrivate);` – jscs Jan 14 '14 at 01:35
1

Seems odd, putting iVars in the `@interface` seems to be a deprecated pattern. – Abizern Jan 14 '14 at 13:47

score 1 · Answer 2 · edited Jan 14 '14 at 13:37

1

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

edited Jan 14 '14 at 13:37

Abizern

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answered Jan 13 '14 at 23:10

Adnan Aftab

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Analyze definitely needs more awareness – Jack Jan 13 '14 at 23:13

Skotch · Answer 3 · 2014-01-14T00:07:09.733

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.

How to find unused ivars in Xcode

3 Answers3