Drawing two objects in separate files - objective-c

Question

Player.m
//
// PlayerTestAppDelegate.m
// PlayerTest
//
// Created by Someguy on 5/13/11.
// Copyright 2011 Enginering. All rights reserved.
//
#import "Player.h"
#implementation Player
#synthesize window;
//[NSThread sleepForTimeInterval:.1];
// On the program finished loading, do the following..
- (void)applicationDidFinishLaunching:(NSNotification *)aNotification {plyr_size = 10; xcord = 200; ycord = 215; [self DrawPlayer];}
- (void)Clearscreen{NSPoint origin = {0,0}; NSRect rect; rect.origin = origin; rect.size.width=1000; rect.size.height=1000; NSBezierPath * path; path = [NSBezierPath bezierPathWithRect:rect]; [path setLineWidth:4]; [[NSColor whiteColor] set]; [path fill]; [[NSColor whiteColor] set]; [path stroke];}
- (void)DrawPlayer{[self Clearscreen]; NSBezierPath * path = [NSBezierPath bezierPath]; [path setLineWidth:4]; NSPoint center = {ycord,xcord}; [path moveToPoint: center]; [path appendBezierPathWithArcWithCenter: center radius: plyr_size startAngle: 0 endAngle: 360]; [[NSColor grayColor] set]; [path fill]; [[NSColor grayColor] set]; [path stroke];}
//Declare these actions
- (IBAction)PlayerMoveForward:(id)sender {[self PlayerMoveForward];}
- (IBAction)PlayerMoveBackwards:(id)sender {[self PlayerMoveBackwards];}
- (IBAction)PlayerMoveLeft:(id)sender {[self PlayerMoveLeft];}
- (IBAction)PlayerMoveRight:(id)sender {[self PlayerMoveRight];}
// Declare the Methods used for movement
- (void)PlayerMoveForward {xcord=xcord+10; [self DrawPlayer]; [self GetPlayerPostion];}
- (void)PlayerMoveBackwards {xcord=xcord-10; [self DrawPlayer]; [self GetPlayerPostion];}
- (void)PlayerMoveLeft {ycord=ycord-10; [self DrawPlayer]; [self GetPlayerPostion];}
- (void)PlayerMoveRight {ycord=ycord+10; [self DrawPlayer]; [self GetPlayerPostion];}
- (void)GetPlayerPostion {NSLog(#"Player cordinates (%i, %i)",xcord, ycord);}
#end
EntityZombie.m
//
// EntityZombie.m
// PlayerTest
//
// Created by Someguy on 5/13/11.
// Copyright 2011 Enginering. All rights reserved.
//
#import "EntityZombie.h"
#import "Player.h"
#implementation EntityZombie : Player
//- (void)applicationDidFinishLaunching:(NSNotification *)aNotification {[self FollowPlayer];}
- (void)awakeFromNib{[self FollowPlayer];}
- (void)DrawZombie {if ([self CanSpawnZombie] == TRUE){NSBezierPath * path = [NSBezierPath bezierPath]; [path setLineWidth:4]; NSPoint center = {215,200}; [path moveToPoint: center]; [path appendBezierPathWithArcWithCenter: center radius: 18 startAngle: 0 endAngle: 360]; [[NSColor greenColor] set]; [path fill]; [[NSColor greenColor] set]; [path stroke];}}
- (void)FollowPlayer {
NSLog(#"Zombie is following player..");
//zombie_xcord == xcord-1;
//zombie_ycord == ycord-1;
[self DrawZombie];
}
- (BOOL)CanSpawnZombie{return TRUE;}
#end
The zombie will not render and I have the log of
2011-05-13 20:59:22.677 PlayerTest[45207:a0f] Zombie is following player..
Fri May 13 20:59:22 Someguy-MacBook-Pro.local PlayerTest[45207] <Error>: CGContextSetFillColorWithColor: invalid context 0x0

Answer 1

There is no current draw context. The issue is from where you are calling the draw methods. They need to be called from a -(void) drawRect method or, if you'd prefer, you can draw into an image. Either way, there has to be a current draw context.