No you can’t. Go is a static typed language. The type of a variable is determined at compile time. If you want to determine dynamically the typeof an interface{} you could use type switching: var t interface{} t = functionOfSomeType() switch t := t.(type) { default: fmt.Printf(“unexpected type %T”, t) // %T prints whatever type … Read more
Declare is mainly useful for mocking values when playing around with the type system. In production code, it’s rarely used. declare name: string; This says to the compiler: “There is a property called name of type string. I shouldn’t have to prove to you that name actually exists, but I want to use it anyway.” … Read more
A type assertion asserts that t (an interface type) actually is a aType and t will be an aType; namely the one wrapped in the t interface. E.g. if you know that your var reader io.Reader actually is a *bytes.Buffer you can do var br *bytes.Buffer = reader.(*bytes.Buffer). A type conversion converts one (non-interface) type … Read more
It is very easy to write a Benchmark test to check it: http://play.golang.org/p/E9H_4K2J9- package main import ( “testing” ) type myint int64 type Inccer interface { inc() } func (i *myint) inc() { *i = *i + 1 } func BenchmarkIntmethod(b *testing.B) { i := new(myint) incnIntmethod(i, b.N) } func BenchmarkInterface(b *testing.B) { i := … Read more
sess.Values[“user”] is an interface{}, and what is between parenthesis is called a type assertion. It checks that the value of sess.Values[“user”] is of type bson.ObjectId. If it is, then ok will be true. Otherwise, it will be false. For instance: var i interface{} i = int(42) a, ok := i.(int) // a == 42 and … Read more
This is known as a const assertion. A const assertion tells the compiler to infer the narrowest* or most specific type it can for an expression. If you leave it off, the compiler will use its default type inference behavior, which will possibly result in a wider or more general type. Note that it is … Read more
TypeScript uses ‘<>’ to surround casts, so the above becomes: var script = <HTMLScriptElement>document.getElementsByName(“script”)[0]; However, unfortunately you cannot do: var script = (<HTMLScriptElement[]>document.getElementsByName(id))[0]; You get the error Cannot convert ‘NodeList’ to ‘HTMLScriptElement[]’ But you can do : (<HTMLScriptElement[]><any>document.getElementsByName(id))[0];