如何解决使用反射获取实现接口的所有类,并且仅初始化与给定ID /操作码匹配的类
因此,在下面的代码中,有一个指令接口,该接口被许多类(例如AddInstruction,DivideInstruction等)使用。实现该接口的每个类都按照Instruction接口分配标签和操作码。
Instruction.cs
public abstract class Instruction
{
private string label;
private string opcode;
protected Instruction(string label,string opcode)
{
this.label = label;
this.opcode = opcode;
}
public abstract void Execute(Machine m);
}
所有指令均具有相同基本功能的众多指令之一的示例
AddInstruction.cs
public class AddInstruction : Instruction
{
private int reg,s1,s2;
public AddInstruction(string lab,int reg,int s1,int s2) : base(lab,"add") // here the base interface is Instruction and we are assigning the opcode as add,other instructions have there own opcodes //
{
this.reg = reg;
this.s1 = s1;
this.s2 = s2;
}
public override void Execute(Machine m) =>
// do something
}
从这里开始,我想将工厂模式与Reflection一起使用,以便将来可以根据提供的操作码来启动具有自己操作码的新指令。
InstructionFactoryInterface.cs
interface InstructionFactoryInterface
{
Instruction GetInstruction(string opcode);
}
InstructionFactory.cs
class InstructionFactory : InstructionFactoryInterface
{
public Instruction GetInstruction(string opcode)
{
Type type = typeof(Instruction);
var types = AppDomain.CurrentDomain.GetAssemblies()
.SelectMany(s => s.GetTypes())
.Where(p => type.IsAssignableFrom(p));
foreach (var type1 in types)
{
// loop through all the types and only return the class that has a matching opcode //
}
}
现在这是我很烂的地方,我如何遍历实现Instruction接口的所有类型,而只返回与传入的opcode参数匹配的类型。谢谢
解决方法
使用字典和将已知操作与工厂方法(或委托)一起注册更容易
public static Dictionary<string,Func<string,int,Instruction>> FactoryDict
{ get; } = new Dictionary<string,Instruction>> {
["add"] = (lab,reg,s1,s2) => new AddInstruction(lab,s2),["sub"] = (lab,s2) => new SubInstruction(lab,//...
};
请注意,您不必使用所有参数:
["nop"] = (lab,s2) => new NopInstruction(lab,reg),
然后您可以通过获取说明
public Instruction GetInstruction(string opcode,string lab,int reg,int s1,int s2)
{
if (FactoryDict.TryGetValue(opcode,out var create)) {
return create(lab,s2);
}
return null;
}
如果您使用命名约定,例如指令类的名称是带有大写首字母+“指令”的操作码:
public Instruction GetInstruction(string opcode,int s2)
{
// E.g. make "AddInstruction" out of "add"
string instructionName = $"{Char.ToUpper(opcode[0])}{opcode.Substring(1)}Instruction";
Type baseType = typeof(Instruction);
Type instructionType = AppDomain.CurrentDomain.GetAssemblies()
.SelectMany(s => s.GetTypes())
.Where(p => baseType.IsAssignableFrom(p) &&
!p.IsAbstract &&
p.Name == instructionName)
.FirstOrDefault();
if (instructionType != null) {
return (Instruction)Activator.CreateInstance(instructionType,lab,s2);
}
return null;
}
此外,始终使用标准化参数列表的构造函数会使事情变得更容易。
,这有点棘手,因为AddInstruction
没有默认的构造函数。话虽如此,它可以做到。您将需要使用FormatterServices.GetUninitializedObject()
来获取实例,而无需使用构造函数。基类Instruction
也将需要修改,因此opcode
不是字段,而是在每个子类中实现的方法。这是一个示例:
using System;
using System.Runtime.Serialization;
namespace Generator
{
public class Program
{
public static void Main()
{
var add = FormatterServices.GetUninitializedObject(typeof(AddInstruction));
var opcode = ((Instruction) add).GetOpCode();
Console.WriteLine(opcode);
}
}
public abstract class Instruction
{
public abstract string GetOpCode();
}
public class AddInstruction : Instruction
{
private int s1,s2;
public AddInstruction(int s1,int s2)
{
this.s1 = s1;
this.s2 = s2;
}
public override string GetOpCode()
{
return "add";
}
}
}
,
System.Reflection API不允许您从构造函数主体获取IL指令。因此,您无法确定特定类的构造函数将哪个参数传递给基本构造函数。
您可以使用Mono.Cecil库(也可以与.NET Framework一起使用)完成此任务。
class InstructionFactory : InstructionFactoryInterface {
static readonly IDictionary<string,Type> Instructions = new Dictionary<string,Type>();
static InstructionFactory() {
InitializeDictionary();
}
static void InitializeDictionary() {
Type type = typeof(Instruction);
var types = AppDomain.CurrentDomain.GetAssemblies()
.SelectMany(s => s.GetTypes())
.Where(p => type.IsAssignableFrom(p));
foreach(var type1 in types) {
try {
string type1Opcode = GetOpcode(type1);
Instructions.Add(type1Opcode,type1);
} catch(InvalidOperationException ex) {
LogError(ex);
}
}
}
static void LogError(InvalidOperationException ex) {
// ...
}
public Instruction GetInstruction(string opcode,params object[] args) {
Type instructionType;
bool found = Instructions.TryGetValue(opcode,out instructionType);
if(!found) {
throw new InvalidOperationException($"Instruction {opcode} not found");
}
return (Instruction)Activator.CreateInstance(instructionType,args);
}
static readonly IDictionary<string,AssemblyDefinition> AssemblyDefinitions = new Dictionary<string,AssemblyDefinition>();
static AssemblyDefinition GetAssemblyDefinition(Type type) {
AssemblyDefinition ad;
bool found = AssemblyDefinitions.TryGetValue(type.Assembly.Location,out ad);
if(!found) {
ad = AssemblyDefinition.ReadAssembly(type.Assembly.Location);
AssemblyDefinitions.Add(type.Assembly.Location,ad);
}
return ad;
}
static string GetOpcode(Type type) {
AssemblyDefinition adType = GetAssemblyDefinition(type);
TypeDefinition tdType = adType.MainModule.GetType(type.FullName);
IEnumerable<MethodDefinition> ctors = tdType.GetConstructors();
AssemblyDefinition adInstruction = GetAssemblyDefinition(typeof(Instruction));
TypeDefinition tdInstruction = adInstruction.MainModule.GetType(typeof(Instruction).FullName);
MethodDefinition ctorInstruction = tdInstruction.GetConstructors().Single();
foreach(MethodDefinition ctor in ctors) {
for(int i = 0; i < ctor.Body.Instructions.Count; i++) {
Mono.Cecil.Cil.Instruction instr = ctor.Body.Instructions[i];
if(instr.OpCode.Code == Code.Call && instr.Operand is MethodDefinition md && md == ctorInstruction) {
Mono.Cecil.Cil.Instruction lastParameter = ctor.Body.Instructions[i - 1];
return (string)lastParameter.Operand;
}
}
}
throw new InvalidOperationException($"{type.FullName} does not call the base constructor");
}
}
,
如何使用属性?对于未来,它是非常可扩展的。尽管由于您的操作码只是一个字符串,所以您在字符串比较和唯一性方面都必须谨慎,因为将来您最终可能会遇到两个共享相同操作码的类。
自定义属性类:
[Instruction("the opCode associated with this type")]
public class AddInstruction : Instruction
{
// rest of class
}
标记派生类:
class InstructionFactory : InstructionFactoryInterface
{
public Instruction GetInstruction(string opcode)
{
Type type = typeof(Instruction);
var types = AppDomain.CurrentDomain.GetAssemblies()
.SelectMany(s => s.GetTypes())
.Where(p => type.IsAssignableFrom(p));
foreach (var type1 in types)
{
var att = type1.GetCustomAttribute<InstructionAttribute>(false); // don't check ancestors; only this type
string attributeOpCode = att?.OpCode;
if (!string.IsNullOrWhiteSpace(attributeOpCode) && attributeOpCode == opcode)
{
// construct an instance of type1 however you prefer,return it
}
}
return null; // or other error handling
}
}
更改为使用该属性来查找所需类型的InstructionFactory:
sign_in_button1=driver.find_element_by_xpath('''/html/body/div[8]/div[3]/div/div/div/div/div[2]/main/div[1]/section/div[2]/div[1]/div[1]/div/div/img''')
此后,您可以添加任意数量的从Instruction派生的新类-您只需为它们分配要用作标识符的操作码字符串即可。
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