我正在使用一个可怕的黑客来填充XNA框架中的锁定数据类型:我希望在不给垃圾收集器提供的情况下调用结构中的内部方法。
如果我将所述结构保存在一个对象变量中并使用MethodInfo.Invoke()
,那么该调用本身会通过装箱参数来提供垃圾收集器:
private object boxedTouchCollection;
void test() {
MethodInfo addTouchLocationMethod = typeof(TouchCollection).GetMethod(
"AddTouchLocation", BindingFlags.Instance | BindingFlags.NonPublic
);
addTouchLocationMethod.Invoke(
this.boxedState, new object[] { /* parameters being boxed */ }
);
}
我不确定这里是否可以使用Delegate.CreateDelegate()
- 我可以将第一个参数转换为一个对象吗?它可以在盒装结构上工作吗?或者我可以将我的结构存储为未装箱并将第一个参数声明为ref TouchCollection
?
delegate void AddTouchLocationDelegate(
ref TouchCollection collection,
int id,
// ...more parameters...
);
private TouchCollection touchCollection;
void test() {
Delegate.CreateDelegate(
typeof(AddTouchLocationDelegate),
typeof(ref TouchCollection), // doesn't compile
addTouchLocationMethod
);
}
我可以让Delegate.CreateDelegate()
工作吗?
或者我是否必须采用动态IL生成?
答案 0 :(得分:3)
这是一种方式。
它依赖于Delegate.CreateDelegate
public struct Foo
{
// Internal method to be called. Takes a value-type parameter.
internal void Test(int someParam)
{
Console.WriteLine(someParam);
}
// Custom delegate-type. Takes the Foo instance of interest
// by reference, as well as the argument to be passed on to Test.
public delegate void MyDelegate(ref Foo foo, int someParam);
// Creates type-safe delegate
private static MyDelegate GetTestDelegate()
{
var flags = BindingFlags.Instance | BindingFlags.NonPublic;
var methodInfo = typeof(Foo).GetMethod("Test", flags);
return (MyDelegate) Delegate.CreateDelegate
(typeof(MyDelegate), methodInfo);
}
static void Main()
{
Foo foo = new Foo();
MyDelegate action = GetTestDelegate();
// should dodge boxing
action(ref foo, 42);
}
}
,它创建了开放的实例方法委托。唯一棘手的一点是,所以你必须创建适当的委托类型才能通过引用传递结构。
我不认为应该有这种技术的装箱 - 要么是方法的参数,要么是结构本身。
示例:(用于简化示例类型的道歉)
{{1}}
答案 1 :(得分:1)
这是我在此期间使用Linq Expression Trees的另一个解决方案:
private delegate void AddTouchLocationDelegate(
ref TouchCollection touchCollection,
int id,
TouchLocationState state,
float x,
float y,
TouchLocationState prevState,
float prevX,
float prevY
);
private static AddTouchLocationDelegate createAddTouchLocationDelegate() {
MethodInfo addTouchLocationMethod = typeof(TouchCollection).GetMethod(
"AddTouchLocation", BindingFlags.Instance | BindingFlags.NonPublic
);
Type byrefTouchCollection = typeof(TouchCollection).MakeByRefType();
ParameterExpression instance = Expression.Parameter(byrefTouchCollection, "instance");
ParameterExpression idValue = Expression.Parameter(typeof(int), "id");
ParameterExpression stateValue = Expression.Parameter(
typeof(TouchLocationState), "state"
);
ParameterExpression xValue = Expression.Parameter(typeof(float), "x");
ParameterExpression yValue = Expression.Parameter(typeof(float), "y");
ParameterExpression prevStateValue = Expression.Parameter(
typeof(TouchLocationState), "prevState"
);
ParameterExpression prevXValue = Expression.Parameter(typeof(float), "prevX");
ParameterExpression prevYValue = Expression.Parameter(typeof(float), "prevY");
Expression<AddTouchLocationDelegate> expression =
Expression.Lambda<AddTouchLocationDelegate>(
Expression.Call(
instance, addTouchLocationMethod,
idValue, stateValue, xValue, yValue, prevStateValue, prevXValue, prevYValue
),
instance,
idValue, stateValue, xValue, yValue, prevStateValue, prevXValue, prevYValue
);
return expression.Compile();
}
用法很简单:
var d = createAddTouchLocationDelegate();
d(
ref this.touches,
1, TouchLocationState.Pressed, 10, 10, TouchLocationState.Released, 0, 0
);