Why a use of undeclared identifier? - ios

Question

Why does my code say I'm using an undeclared identifier with 'hero' in shootAt in the line fourth from the end.
#import "GameplayLayer.h"
#import "Ship.h"
#import "MainCharacter.h"
#import "GameOverLayer.h"
int screenHeight;
int screenWidth;
#implementation GameplayLayer
-(id) init
{
if ((self = [super init]))
{
screenHeight = [[CCDirector sharedDirector] screenSize].height;
screenWidth = [[CCDirector sharedDirector] screenSize].width;
MainCharacter * hero = [[MainCharacter alloc] init];
[self addChild: hero];
hero.position = ccp(screenWidth/2, screenHeight/10);
Ship * ship1 = [[Ship alloc] init];
[self addChild: ship1];
numEnemies++;
ship1.position = ccp(screenWidth/2, screenHeight/2);
}
return self;
[self scheduleUpdate];
}
-(void) update: (ccTime) dt
{
KKInput * input = [KKInput sharedInput];
CGPoint touchPosition = [input locationOfAnyTouchInPhase:KKTouchPhaseBegan];
if (touchPosition.x != 0.0 || touchPosition.y != 0.0)
{
[hero shootAt: ccp(screenWidth/2, screenHeight)];
}
}
#end

Answer 1

Because hero is local variable defined in the constructor and hence not visible in other methods.

Answer 2

I think this is the problem of scope of variable, You declared
hero
in your
init Method
and trying to access this variable in
update Method (So hero is a local variable for init Method and undeclared for Update Method).
Update your code Like this, If you want a global Access of
hero object,
int screenHeight;
int screenWidth;
MainCharacter * hero;
And then initialize it in your init Method and access it in all other methods of same class.