你不能做你想做的事,但是有一种相对简单的方法可以通过从不同的方向进入来达到相同的结果
字符串不唯一标识类型
这是将字符串转换为类型的基本问题:当您看到 a 时T
,您不知道它是从哪里来的。以下是一个有效的类定义:
class Simple<T> {
public T Make(T blah) {
return blah;
}
public T Make<T>(T blah) {
return blah;
}
}
的两个重载Make
具有看起来相同的参数,但它们的比较并不相等。此外,如果不首先获得T
泛型,就绝对无法获得泛型的—— 循环依赖。Make<T>
MethodInfo
Make<T>
你能做什么?
您可以构建一个匹配器来告诉您一个类型的实例(包括无界泛型类型)是否匹配给定的字符串表示,而不是进行不可能的string
->转换:Type
static bool MatchType(string str, Type type)
使用此方法,您可以浏览所有具有特定名称的可用方法,并根据字符串数组中的字符串逐一检查其参数列表的类型:
var typesAsStr = new [] {"T", "List`1[T]", "List`1[Tuple`2[T, string]]"};
var myMethod = typeof (Simple<>)
.GetMethods()
.SingleOrDefault(m => m.Name == "MyMethod" &&
typesAsStr
.Zip(m.GetParameters(), (s, t) => new {s, t})
.All(p => MatchType(p.s, p.t.ParameterType))
);
你如何实现该MatchType
方法?
您可以使用类似于Recursive Descent Parsing的技术:标记您的字符串,然后在遍历标记链时匹配您类型的元素。当一个类被参数化时,获取泛型参数并递归匹配它们。您需要注意数组类型,但这也相对简单。看一看:
public static bool MatchType(string str, Type type) {
var queue = new Queue<Token>(Tokenize(str));
return MatchRecursive(queue, type) && (queue.Count == 0);
}
private static bool MatchRecursive(Queue<Token> tokens, Type type) {
string baseName;
if (!ReadToken(tokens, TokenType.Identifier, out baseName)) return false;
var ranks = new List<int>();
while (type.IsArray) {
ranks.Add(type.GetArrayRank());
type = type.GetElementType();
}
if (type.IsGenericType) {
if (!type.Name.StartsWith(baseName+"`") || !DropToken(tokens, TokenType.Tick)) return false;
string numStr;
int num;
if (!ReadToken(tokens, TokenType.Number, out numStr)
|| !int.TryParse(numStr, out num)
|| !DropToken(tokens, TokenType.OpenBraket)) return false;
var genParams = type.GetGenericArguments();
if (genParams.Length != num) return false;
for (var i = 0 ; i < num ; i++) {
if (i != 0 && !DropToken(tokens, TokenType.Comma)) return false;
if (!MatchRecursive(tokens, genParams[i])) return false;
}
if (!DropToken(tokens, TokenType.CloseBraket)) return false;
}
foreach (var rank in ranks) {
if (!DropToken(tokens, TokenType.OpenBraket)) return false;
for (var i = 0 ; i != rank-1 ; i++) {
if (!DropToken(tokens, TokenType.Comma)) return false;
}
if (!DropToken(tokens, TokenType.CloseBraket)) return false;
}
return type.IsGenericType || Aliases.Contains(new Tuple<string, Type>(baseName, type)) || type.Name == baseName;
}
private static readonly ISet<Tuple<string,Type>> Aliases = new HashSet<Tuple<string, Type>> {
new Tuple<string, Type>("bool", typeof(bool)),
new Tuple<string, Type>("byte", typeof(byte)),
new Tuple<string, Type>("sbyte", typeof(sbyte)),
new Tuple<string, Type>("char", typeof(char)),
new Tuple<string, Type>("string", typeof(string)),
new Tuple<string, Type>("short", typeof(short)),
new Tuple<string, Type>("ushort", typeof(ushort)),
new Tuple<string, Type>("int", typeof(int)),
new Tuple<string, Type>("uint", typeof(uint)),
new Tuple<string, Type>("long", typeof(long)),
new Tuple<string, Type>("ulong", typeof(ulong)),
new Tuple<string, Type>("float", typeof(float)),
new Tuple<string, Type>("double", typeof(double)),
new Tuple<string, Type>("decimal", typeof(decimal)),
new Tuple<string, Type>("void", typeof(void)),
new Tuple<string, Type>("object", typeof(object))
};
private enum TokenType {
OpenBraket,
CloseBraket,
Comma,
Tick,
Identifier,
Number
}
private class Token {
public TokenType Type { get; private set; }
public string Text { get; private set; }
public Token(TokenType type, string text) {
Type = type;
Text = text;
}
public override string ToString() {
return string.Format("{0}:{1}", Enum.GetName(typeof(TokenType), Type), Text);
}
}
private static bool DropToken(Queue<Token> tokens, TokenType expected) {
return (tokens.Count != 0) && (tokens.Dequeue().Type == expected);
}
private static bool ReadToken(Queue<Token> tokens, TokenType expected, out string text) {
var res = (tokens.Count != 0) && (tokens.Peek().Type == expected);
text = res ? tokens.Dequeue().Text : null;
return res;
}
private static IEnumerable<Token> Tokenize(IEnumerable<char> str) {
var res = new List<Token>();
var text = new StringBuilder();
foreach (var c in str) {
var pos = "[],`".IndexOf(c);
if ((pos != -1 || char.IsWhiteSpace(c)) && text.Length != 0) {
res.Add(new Token(
char.IsDigit(text[0]) ? TokenType.Number : TokenType.Identifier
, text.ToString())
);
text.Clear();
}
if (pos != -1) {
res.Add(new Token((TokenType)pos, c.ToString(CultureInfo.InvariantCulture)));
} else if (!char.IsWhiteSpace(c)) {
text.Append(c);
}
}
if (text.Length != 0) {
res.Add(new Token(
char.IsDigit(text[0]) ? TokenType.Number : TokenType.Identifier
, text.ToString())
);
}
return res;
}