public Expression Build(Expression element, MethodInfo method)
{
var type = method.DeclaringType;
if (method.ReturnType != typeof(void) && method.ReturnType != typeof(EffectCleanupDelegate))
{
throw new ArgumentException($"Effect method {method} in {type} returns unsupported type {method.ReturnType}. It must return either void or {nameof(EffectCleanupDelegate)}.");
}
// find dependency fields
var fields = new FieldInfo[_depFields.Length];
for (var i = 0; i < _depFields.Length; i++)
{
fields[i] = type?.GetAllField(_depFields[i]) ?? throw new ArgumentException($"Cannot find field '{_depFields[i]}' in {type}.");
}
// find parameter providers
var parameters = method.GetParameters();
var arguments = new Expression[parameters.Length];
for (var i = 0; i < parameters.Length; i++)
{
arguments[i] = parameters[i].GetCustomAttributes().OfType <IBinderMethodParameterProvider>().FirstOrDefault()?.GetValue(element, parameters[i]) ?? throw new ArgumentException($"No provider configured for parameter {parameters} of method {method} in {type}.");
}
var body = new List <Expression>();
// build dependency array
var deps = Expression.Variable(typeof(object[]), "deps");
if (Once)
{
body.Add(Expression.Assign(deps, Expression.Constant(null, typeof(object[]))));
}
else
{
var items = new Expression[fields.Length + arguments.Length];
for (var i = 0; i < fields.Length; i++)
{
items[i] = Expression.Field(element, fields[i]);
}
for (var i = 0; i < arguments.Length; i++)
{
items[fields.Length + i] = arguments[i];
}
body.Add(Expression.Assign(deps, Expression.NewArrayInit(typeof(object), items.Select(x => Expression.Convert(x, typeof(object))))));
}
// create effect info
var effect = Expression.Variable(typeof(RefObject <EffectInfo>), "effectObj");
body.Add(Expression.Assign(effect, ElementBinder.BuildContainerInstantiation(typeof(RefObject <EffectInfo>), element, Expression.Constant($"effect:{method.Name}"), null)));
// call effect set method
body.Add(Expression.Call(
Expression.Coalesce(
ElementBinder.BuildContainerValueAccess(effect),
Expression.Assign(ElementBinder.BuildContainerValueAccess(effect), Expression.New(typeof(EffectInfo)))),
_effectInfoSetMethod,
ElementBinder.BuildElementNodeAccess(element),
Expression.Lambda <EffectDelegate>(buildEffect()),
deps));
Expression buildEffect()
{
var result = Expression.Call(element, method, arguments);
if (method.ReturnType == typeof(EffectCleanupDelegate))
{
return(result);
}
return(Expression.Block(result, Expression.Constant(null, typeof(EffectCleanupDelegate))));
}
return(Expression.Block(new[] { deps, effect }, body));
}