headers.md

Headers

In objective-c, headers contain our methods and as you will remember our methods allow us to change and modify code on our device

What Does A Header Look Like

This is the header for SBVolumeControl.h as we found in our previous lesson

#import <SpringBoard/SpringBoard-Structs.h>
#import <libobjc.A.dylib/SBVolumeHUDViewControllerDelegate.h>
#import <libobjc.A.dylib/PTSettingsKeyObserver.h>
#import <libobjc.A.dylib/SBAVSystemControllerCacheObserver.h>

@protocol OS_dispatch_queue;
@class SBHUDController, SBVolumeHUDSettings, SBRingerControl, NSMutableArray, NSMutableSet, NSString, NSObject, SBAVSystemControllerCache, NSArray;

@interface SBVolumeControl : NSObject <SBVolumeHUDViewControllerDelegate, PTSettingsKeyObserver, SBAVSystemControllerCacheObserver> {

+(id)sharedInstance;
+(BOOL)_isVolumeChangeAllowedForState:(id)arg1 error:(out id*)arg2 ;
-(float)_effectiveVolume;
-(void)settings:(id)arg1 changedValueForKey:(id)arg2 ;
-(void)increaseVolume;
-(void)decreaseVolume;
-(void)cancelVolumeEvent;
-(void)handleVolumeButtonWithType:(long long)arg1 down:(BOOL)arg2 ;


...

}

@end

This header file is a lot bigger and the rest of it is hidden for the purpose of the guide. Please remember in practice header files can be massive but they can also be relatively small

So you first impression is probably... what the hell is that. Well the good news is we don't need to worry about the majority of it.

Exactly How Do We Use them

Well first, the site has a handy button right next to it called logify this automatically converts the header into logos syntax

So if we press that button it will give us this

%hook SBVolumeControl
+(id)sharedInstance { %log; id r = %orig; HBLogDebug(@" = %@", r); return r; }
+(BOOL)_isVolumeChangeAllowedForState:(id)arg1 error:(out id*)arg2  { %log; BOOL r = %orig; HBLogDebug(@" = %d", r); return r; }
-(float)_effectiveVolume { %log; float r = %orig; HBLogDebug(@" = %f", r); return r; }
-(void)settings:(id)arg1 changedValueForKey:(id)arg2  { %log; %orig; }
-(void)increaseVolume { %log; %orig; }
-(void)decreaseVolume { %log; %orig; }
-(void)cancelVolumeEvent { %log; %orig; }
-(void)handleVolumeButtonWithType:(long long)arg1 down:(BOOL)arg2  { %log; %orig; }

...

%end

Again this file is bigger just like the header but is hidden for the sake of the guide

Now this will look a bit more familiar, but again we don't need to worry about most of it

logify automatically gives us the correct hook and class so we don't need to worry about that

So if we have our hook and our class the only missing thing is our method

Lets scroll through the code logify has given us and see if anything stands out

-(void)increaseVolume { %log; %orig; }
-(void)decreaseVolume { %log; %orig; }

Now these two methods seem like they control volume, which is perfect and exactly what we want.

So lets make the hook smaller as we don't need the rest of the methods

%hook SBVolumeControl
-(void)increaseVolume { %log; %orig; }
-(void)decreaseVolume { %log; %orig; }
%end

Now thats a lot more manageable, but we can still trim it down a bit, lets format it So we can read it a lot better

%hook SBVolumeControl

-(void)increaseVolume {
	%log;
	%orig;
}

-(void)decreaseVolume {
	%log;
	%orig;
}

%end

If we really wanted to trim it down more we can remove the %log as I will show you another method of debugging

%hook SBVolumeControl

-(void)increaseVolume {
	%orig;
}

-(void)decreaseVolume {
	%orig;
}

%end

Now thats, way easier to understand. So lets put it together.