////  main.m//  Hello////  Created by lishujun on 14-8-28.//  Copyright (c) 2014年 lishujun. All rights reserved.//#import <UIKit/UIKit.h>// 视图控制器对象@interface HelloWorldViewController : UIViewController@end@implementation HelloWorldViewController-(void) loadView{    /*     self.view = contentView;      [self setView contentView];     等价，设置属性其实是调用set方法     */        //创建视图对象    UIView *contentView = [[UIView alloc]initWithFrame:[[UIScreen mainScreen] applicationFrame]];    NSLog(@"new contentView : %d", [contentView retainCount]);  // new contentView : 1    contentView.backgroundColor = [UIColor lightGrayColor];    NSLog(@"set contentView : %d", [contentView retainCount]);  // set contentView : 1    [self setView: contentView];     NSLog(@"add contentView : %d", [contentView retainCount]); // add contentView : 2        //创建label对象    UILabel *label = [[UILabel alloc]initWithFrame:CGRectMake(0.0, 0.0, 320.0, 30.0)];    NSLog(@"new label : %d", [label retainCount]);              // new label : 1    label.text = @"Hello World";    label.center = contentView.center;    label.textAlignment = UITextAlignmentCenter;    label.backgroundColor = [UIColor clearColor];    label.textColor = [UIColor redColor];    NSLog(@"set label : %d", [label retainCount]);              // set label : 1        //在视图上添加label    [contentView addSubview:label];    NSLog(@"add label : %d", [label retainCount]);              // add label : 2    [label release];     NSLog(@"release label : %d", [label retainCount]);         // release label : 1    }@end// 委托对象@interface HelloWorldAppDelegate : NSObject <UIApplicationDelegate>{    IBOutlet UIWindow *window;}@property (nonatomic, retain) UIWindow *window;@property (nonatomic, retain) HelloWorldViewController *viewController;//window 必须声明为属性,声明为局部变量则无法绘制视图，显示为黑屏//apple 官方文档把viewController也声明为属性了@end@implementation HelloWorldAppDelegate@synthesize window;@synthesize viewController;-(void) applicationDidFinishLaunching:(UIApplication *)application{    self.window = [[UIWindow alloc] initWithFrame:[[UIScreen mainScreen]bounds]];    self.viewController = [[HelloWorldViewController alloc]init];    self.window.rootViewController = self.viewController;    [self.window makeKeyAndVisible];}@end// 程序入口int main(int argc, char * argv[]){    @autoreleasepool {        return UIApplicationMain(argc, argv, nil, @"HelloWorldAppDelegate");    }}

2014-08-30 11:47:30.980 HelloNOARC[562:60b] new contentView : 12014-08-30 11:47:30.983 HelloNOARC[562:60b] set contentView : 12014-08-30 11:47:30.984 HelloNOARC[562:60b] add contentView : 22014-08-30 11:47:30.985 HelloNOARC[562:60b] new label : 12014-08-30 11:47:30.986 HelloNOARC[562:60b] set label : 12014-08-30 11:47:30.986 HelloNOARC[562:60b] add label : 22014-08-30 11:47:30.987 HelloNOARC[562:60b] release label : 1