Golang: print struct as it would appear in source code

Question

Similar to this question but not quite identical.

I'm doing some code-generation, making .go files from within Go. I've got a struct, and I want to generate the text representation of it so that I can insert it as a literal into the generated code.

So, if I had myVal := SomeStruct{foo : 1, bar : 2}, I want to get the string "SomeStruct{foo : 1, bar : 2}".

Is this possible in Go?

Thoughtful

Answer 1

From the fmt package:

%#v   a Go-syntax representation of the value

This is as close as you can come with built-in formatting, after removing the package identifier (main. in this example) from the output.

type T struct {
    A string
    B []byte
}

fmt.Printf("%#v\n", &T{A: "hello", B: []byte("world")})

// out
// &main.T{A:"hello", B:[]uint8{0x77, 0x6f, 0x72, 0x6c, 0x64}}

Run

Jessjessa

I tried this, but when I've got type Foo string and {field : Foo("Bar")}, it just prints this to {field : "Bar"}. Any workarounds for this? – Thoughtful

@jmite: what is the type of field in the struct? – Jessjessa

It's type Foo – Thoughtful

@jmite: then the type conversion is superfluous, since the string literal can be assigned to the Foo type. – Jessjessa

@jmite: this still can't do everything, nested pointers are only going to be printed as %p with a type, and values assigned to an interface will only show the underlying type. If you want more detailed output, you need to format it manually. – Jessjessa

Looks like the solution is to implement the GoString() method, described in the fmt library, thanks! – Thoughtful

Ugh...Correction, this is working for map as well, my IDE terminal is stupid and did not print it as a string. Thanks – Pectize

Is it possible to avoid printing the package name? (in this example print only &T{A:"hello", B:[]uint8{0x77, 0x6f, 0x72, 0x6c, 0x64}} – Windy