iOS 分类属性实现懒加载
(用途: 项目重构, 继承->组合)

//UIViewController+AddView.h
#import <UIKit/UIKit.h>

NS_ASSUME_NONNULL_BEGIN

@interface UIViewController (AddView)

@property (nonatomic, strong, readonly) UITableView *tbView;

@end

NS_ASSUME_NONNULL_END


//UIViewController+AddView.m
#import "UIViewController+AddView.h"
#import <objc/runtime.h>

@implementation UIViewController (AddView)

- (UITableView *)tbView{
    id obj = objc_getAssociatedObject(self, _cmd);
    if (obj) {
        return obj;
    }
    UITableView *table = [[UITableView alloc] initWithFrame:CGRectZero style:UITableViewStylePlain];
    [table registerClass:[UITableViewCell class] forCellReuseIdentifier:@"UITableViewCell"];
    table.estimatedRowHeight = 0;
    table.estimatedSectionHeaderHeight = 0;
    table.estimatedSectionFooterHeight = 0;

    if ([self conformsToProtocol:@protocol(UITableViewDataSource)]) table.dataSource = self;
    if ([self conformsToProtocol:@protocol(UITableViewDelegate)]) table.delegate = self;

    objc_setAssociatedObject(self, _cmd, table, OBJC_ASSOCIATION_RETAIN_NONATOMIC);
    return table;
}

🌰🌰：

#import "EntryViewController.h"

@interface EntryViewController ()<UITableViewDataSource, UITableViewDelegate>

@end

@implementation EntryViewController

- (void)viewDidLoad {
    [super viewDidLoad];
    // Do any additional setup after loading the view.
    [self.view addSubview:self.tbView];
}