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Calling dynamically some methods from structs in runtime without know actually the struct to run
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| // Example in The Go Playground: https://play.golang.org/p/huKjmMv--Fs | |
| package main | |
| import ( | |
| "fmt" | |
| "reflect" | |
| "runtime" | |
| "errors" | |
| ) | |
| // These two come from a different package | |
| type One struct{} | |
| type Two struct{} | |
| type Three struct{} | |
| // With this method does not run | |
| func (o *One) Method1(t *Two) {} | |
| // With this method runs, but I can modify the firm of the method because is in another package | |
| // that my code has a dependency | |
| //func (o *One) Method1(t Two) {} | |
| // For testing purposes just comment out the first Method1 and use the second one | |
| // and you can see that the code runs without panic | |
| // In my project I do this | |
| // types.go | |
| type typeRegister map[string]reflect.Type | |
| func (t typeRegister) Set(i interface{}) { | |
| typ := reflect.TypeOf(i).Elem() | |
| t[typ.Name()] = typ | |
| } | |
| func (t typeRegister) Get(name string) (interface{}, error) { | |
| if typ, ok := t[name]; ok { | |
| return reflect.New(typ).Elem().Interface(), nil | |
| } | |
| return nil, errors.New("not valid type registered: " + name) | |
| } | |
| var typeRegistry = make(typeRegister) | |
| func init() { | |
| // These two because they come from another package | |
| // Something like: | |
| // typeRegistry.Set(new(another_package.One)) | |
| // typeRegistry.Set(new(another_package.Two)) | |
| typeRegistry.Set(new(Two)) | |
| typeRegistry.Set(new(Three)) | |
| runtime.GC() | |
| } | |
| // main.go | |
| func main() { | |
| // Dynamically retrieve the string "Two" | |
| // that is the name of the struct to initialize | |
| // in this example a string declarated here | |
| structNameThatIsParameter := "Two" | |
| // Dynamically retrieve the string "Method1" | |
| // that is the name of the method to call on the | |
| // structName value retrieved dynamically | |
| // here, hard coded | |
| methodOfStructInstantiated := "Method1" | |
| i, err := typeRegistry.Get(structNameThatIsParameter) | |
| if err != nil { | |
| // Handle the error, but here just panic | |
| panic(err) | |
| } | |
| // I actually call this because I know what struct I want to call | |
| // In the actual code this is something like: | |
| // instance := new(other_package.One) | |
| instance := new(One) | |
| method := reflect.ValueOf(instance).MethodByName(methodOfStructInstantiated) | |
| // I can't call like this because the firm of the Method1 that is run against | |
| // a pointer to the struct Two | |
| // func (o *One) Method1(t *Two) {} in the package that I'm using | |
| // if the firm of that method is: func (o *One) Method1(t Two) {} | |
| // without a pointer but a struct the method beneath runs | |
| called := method.Call([]reflect.Value{reflect.ValueOf(i)}) | |
| fmt.Printf("%+v\n", called) | |
| } |
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