小编Ton*_*hen的帖子

我有一个嵌入导航控制器的MainViewController,如下所示:

在MainViewController.swift中,我以编程方式添加了两个UIBarButtonItem(左和右):

class MainViewController: UIViewController {

    let rightButton = UIBarButtonItem(title: "Right", style: .plain, target: self, action: #selector(onRightClick))
    let leftButton = UIBarButtonItem(title: "Left", style: .plain, target: self, action: #selector(onLeftClick))

    override func viewDidLoad() {
        super.viewDidLoad()
        navigationItem.rightBarButtonItem = rightButton
        navigationItem.leftBarButtonItem = leftButton
    }

    override func didReceiveMemoryWarning() {
        super.didReceiveMemoryWarning()
    }

    @objc func onRightClick() {
        print("[Main] Right Click")
    }

    @objc func onLeftClick() {
        print("[Main] Left Click")
    }
}

按钮确实显示在屏幕上,但有趣的是,选择器功能onLeftClick,onRightClick每当我按下向左或向右按​​钮时都不会被调用.我有什么办法让它有效吗？我正在使用Xcode 9.3.

我在C中有一个简单的代码,看看三个相同的char数组是否都以'\0':

int main(){
    char a[4] = "1234";
    char b[4] = "1234";
    char c[4] = "1234";


    if(a[4] == '\0')
            printf("a end with '\\0'\n");
    if(b[4] == '\0')
            printf("b end with '\\0'\n");
    if(c[4] == '\0')
            printf("c end with '\\0'\n");

    return 0;
}

但输出显示只有数组b以终结符结束'\0'.这是为什么？我想所有的char数组都必须结束'\0'.

输出:

b以'\ 0'结尾