Question

我正在尝试用Gtk3了解Vala代表。我测试了回调和lambda没有问题。我想测试一个委托回调，这里是我的代码：

using Gtk;

delegate void typeDelegate(Button button);

int main (string[] args) {
    Gtk.init (ref args);
    typeDelegate cb = cbLabelf;
    var window = new Window ();
    window.title = "First GTK+ Program";
    window.border_width = 10;
    window.window_position = WindowPosition.CENTER;
    window.set_default_size (350, 70);
    window.destroy.connect (Gtk.main_quit);

    var button = new Button.with_label ("Click me!");

    //button.clicked.connect (cb);
    //button.clicked+= cb;   
    button.clicked.connect+=cb;

    window.add (button);
    window.show_all ();

    Gtk.main ();
    return 0;
}

void cbLabelf(Button button)
{
 button.label = "tank yu";   


 }

我还用红色生成的C代码（当我使用lambda时）来理解。这里的编译错误：
GTKsampleDelegate.vala：20.5-20.30：错误：类型Gtk.Button.clicked.connect' and typeDelegate'不支持算术运算 button.clicked.connect + = CB;

Answer 1

好吧，

似乎你想获得保存发出信号的实例的内部变量，我发现vala不允许你使用委托变量来通过参数获取它，但是，你可以使用其中一个表单下面：使用无委托变量（A）或使用闭包（B）绕过错误。

public class FooSignalClass : Object {
    /* Gtk Button.clicked signal has the void f(void) signature */
    public signal void on_foo ();
    public void foo() {
        on_foo();
    }
}

public delegate void FooSignalFunc (FooSignalClass fooer);

void on_foo_handler (FooSignalClass fooer) {
    long fooer_memory_address = (long)fooer;
    GLib.message(@"fooer exists? $(fooer!=null).");
    GLib.message(@"address=$fooer_memory_address.");
}

int main () {

    var foo_signal = new FooSignalClass();
    long fooer_memory_address = (long)foo_signal;
    GLib.message(@"foo_signal address=$fooer_memory_address.");

    /* Option A: Connect directly without the delegate variable */
    foo_signal.on_foo.connect(on_foo_handler);

    /* Option B: You cant use a delegate directly, bypass it with a closure */
    FooSignalFunc func = on_foo_handler;
    foo_signal.on_foo.connect((instance) => {
        func(instance);
    });

    foo_signal.foo();

    return 0;
}

如何在GTK3按钮回调中使用VALA代理？

1 个答案: