Vala：在运行时确定List内的泛型类型 [英] Vala: determine generic type inside List at runtime

问题描述

我是Vala的新手，并且玩了一下。目前我正在寻找一种在运行时确定泛型列表的类型参数的方法。

下面的代码使用'反射'来打印Locations类的属性。但是，我无法在运行时确定此列表包含字符串实例。

有没有办法做到这一点？或者在Vala中不支持？

 使用Gee; 
类位置：对象{
 public string numFound {get;组; } 
 public ArrayList< string> docs {get;组; } 
} 
 
 void main（）{
 ObjectClass ocl =（ObjectClass）typeof（Locations）.class_ref（）; 
 ParamSpec [] properties = ocl.list_properties（）; 
 foreach（属性中的ParamSpec spec）{
 string fieldName = spec.get_nick（）; 
 stdout.printf（fieldName：％s\，fieldName）; 
类型fieldType = spec.value_type; 
 stdout.printf（Type：％s\\\
，fieldType.name（））; 
 
 
 $ / code $ / pre 
 $ b $输出：
 
 
  fieldName：numFound 
类型：gchararray 
 fieldName：docs 
类型：GeeArrayList 
  
 
解决方案
没有一种通用的方法可以做到这一点，因为GObject / GType根本不具有表现力。例如，如果您使用的是 GLib.GenericArray （或者 GLib.List ）而不是 Gee.ArrayList 你会不走运。
 
 
 
也就是说，libgee确实提供了一种方法。像大多数libgee中的容器一样， Gee.ArrayList  implements   Gee.Traversable  ，其中包括  element_type  属性。但是请注意，您需要一个实例，而不仅仅是 GLib.ObjectClass 。
 
I am new to Vala and playing around a bit. Currently I am looking for a way to determine the type parameter of a generic list at runtime.

The code below uses 'reflection' to print the properties of the Locations class. However, I am not able to determine at runtime that this list contains instances of string.

Is there a way to do this? Or is this not supported in Vala?
using Gee;
class Locations : Object {
    public string numFound { get; set; }
    public ArrayList<string> docs { get; set; }
}

void main () {
    ObjectClass ocl = (ObjectClass) typeof (Locations).class_ref ();
    ParamSpec[] properties = ocl.list_properties ();
    foreach (ParamSpec spec in properties) {
        string fieldName = spec.get_nick ();
        stdout.printf (" fieldName: %s\n", fieldName);
        Type fieldType = spec.value_type;
        stdout.printf (" Type : %s\n", fieldType.name());
    }
}
Output:
fieldName: numFound
Type : gchararray
fieldName: docs
Type : GeeArrayList

解决方案
There isn't a generic way to do this since GObject/GType simply isn't that expressive.  For example, if you were using a GLib.GenericArray (or a GLib.List) instead of a Gee.ArrayList you would be out of luck.

That said, libgee does provide a way.  Like most containers in libgee, Gee.ArrayList implements Gee.Traversable, which includes the element_type property.  Note, however, that you need an instance, not just the GLib.ObjectClass.

                        
这篇关于Vala：在运行时确定List内的泛型类型的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！