How to Use Reflection to Call Method by Name

How to use reflection to call method by name

Something along the lines of:

MethodInfo method = service.GetType().GetMethod(serviceAction);
object result = method.Invoke(service, new object[] { request });
return (R) result;

You may well want to add checks at each level though, to make sure the method in question is actually valid, that it has the right parameter types, and that it's got the right return type. This should be enough to get you started though.

How do I invoke a Java method when given the method name as a string?

Coding from the hip, it would be something like:

java.lang.reflect.Method method;
try {
  method = obj.getClass().getMethod(methodName, param1.class, param2.class, ..);
} catch (SecurityException e) { ... }
  catch (NoSuchMethodException e) { ... }

The parameters identify the very specific method you need (if there are several overloaded available, if the method has no arguments, only give methodName).

Then you invoke that method by calling

try {
  method.invoke(obj, arg1, arg2,...);
} catch (IllegalArgumentException e) { ... }
  catch (IllegalAccessException e) { ... }
  catch (InvocationTargetException e) { ... }

Again, leave out the arguments in .invoke, if you don't have any. But yeah. Read about Java Reflection

Call methods using names in C#

Sure, you can do it like this:

public class Test
{
    public void Hello(string s) { Console.WriteLine("hello " + s); }
}

...

{
     Test t = new Test();
     typeof(Test).GetMethod("Hello").Invoke(t, new[] { "world" }); 

     // alternative if you don't know the type of the object:
     t.GetType().GetMethod("Hello").Invoke(t, new[] { "world" }); 
}

The second parameter of Invoke() is an array of Object containing all the parameters to pass to your method.

Assuming the methods all belong to the same class, you could have a method of that class something like:

public void InvokeMethod(string methodName, List<object> args)
{
    GetType().GetMethod(methodName).Invoke(this, args.ToArray());
}

Reflection: How to Invoke Method with parameters

Change "methodInfo" to "classInstance", just like in the call with the null parameter array.

  result = methodInfo.Invoke(classInstance, parametersArray);

How to call method by name using Kotlin Reflection?

try this:

obj::class.members.firstOrNull { it.name == "methodName" }?.call(argument1, argument2, ...)

How to use reflection to call a API by string name?

You can use a combination of:

• Type.GetType(string)
• Type.GetMethod(string)
• IIocResolver.ResolveAsDisposable(Type) — by ABP
• MethodInfo.Invoke(Object, Object[])

// var appServiceName = "MyAppService";
// var methodName = "MyMethod";
// var input = new object[] { new MyInput() };

var appServiceType = Type.GetType(appServiceName);
var method = appServiceType.GetMethod(methodName);

using (var appService = IocResolver.ResolveAsDisposable(appServiceType))
{
    var output = await (Task)method.Invoke(appService.Object, input);
}

(Reflection) Calling A Method With Parameters By Function Name In Swift

First of all, as you noted Swift doesn't have full reflection capabilities and rely on the coexisting ObjC to provide these features.

So even if you can write pure Swift code, you will need Solution to be a subclass of NSObject (or implement NSObjectProtocol).

Playground sample:

class Solution: NSObject {

    @objc func functionName(greeting: String, name: String) {
        print(greeting, name)
    }

}

let solutionInstance = Solution() as NSObject
let selector = #selector(Solution.functionName)
if solutionInstance.responds(to: selector) {
    solutionInstance.perform(selector, with: "Hello", with: "solution")
}

There are other points of concern here:

• Swift's perform is limited to 2 parameters
• you need to have the exact signature of the method (#selector here)

If you can stick an array in the first parameters, and alway have the same signature then you're done.
But if you really need to go further you have no choice than to go with ObjC, which doesn't work in Playground.

You could create a Driver.m file of the like:

#import <Foundation/Foundation.h>
#import <objc/runtime.h>

id call (NSObject *callOn, NSString *callMethod, NSArray <NSObject *>*callParameters)
{
    void *result = NULL;
    unsigned int index, count;

    Method *methods = class_copyMethodList(callOn.class, &count);
    for (index = 0; index < count; ++index)
    {
        Method method = methods[index];

        struct objc_method_description *description = method_getDescription(method);
        NSString *name = [NSString stringWithUTF8String:sel_getName(description->name)];
        if ([name isEqualToString:callMethod])
        {
            NSMethodSignature *signature = [NSMethodSignature signatureWithObjCTypes:description->types];
            NSInvocation *invocation = [NSInvocation invocationWithMethodSignature:signature];

            NSObject *parameters[callParameters.count];
            for (int p = 0; p < callParameters.count; ++p) {
                parameters[p] = [callParameters objectAtIndex:p];
                [invocation setArgument:¶meters[p] atIndex:p + 2]; // 0 is self 1 is SEL
            }
            [invocation setTarget:callOn];
            [invocation setSelector:description->name];
            [invocation invoke];
            [invocation getReturnValue:&result];
            break;
        }
    }
    free(methods);

    return (__bridge id)result;
}

Add it to a bridging-header (for Swift to know about what is in ObjC):

// YourProjectName-Bridging-Header.h
id call (NSObject *callOn, NSString *callMethod, NSArray *callParameters);

And call it with a Solution.swift like this:

import Foundation

class Solution: NSObject {

    override init() {
        super.init()
        // this should go in Driver.swift
        let result = call(self, "functionNameWithGreeting:name:", ["Hello", "solution"])
        print(result as Any)
    }

    @objc
    func functionName(greeting: String, name: String) -> String {
        print(greeting, name)
        return "return"
    }

}

output:

Hello solution
Optional(return)

Edit: compilation

To compile both ObjC and Swift on the command line you can first compile ObjC to an object file:

$ cc -O -c YouObjCFile.m

Then compile your Swift project with the bridging header and the object file:

$ swiftc -import-objc-header ../Your-Bridging-Header.h YouObjCFile.o AllYourSwiftFiles.swift -o program

working sample

Using Reflection to call a method of a property

That was quick... I changed the Invoke line to...

m.Invoke(p.GetValue(newControl, null), new object[] { newValue });

...and it worked :P

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