What cases "cannot convert "%d" (type untyped string) to type int" in Go?

Question

package main

import (
    "fmt"
)

func printArray(x [3]int) {
    fmt.Printf("%d", x[1]);
    // cannot convert "%d" (type untyped string) to type int
    // invalid operation: "%d" + v (mismatched types string and int)
    // for _, v := range x {
    //  fmt.Printf("%d" + v);
    // }
}

func main() {
    a := [3]int{1, 2, 3};

    for _, v := range a {
        fmt.Printf("%d\n", v);
    }

    printArray(a); 
}

I can successfully print the array in the go method, but when I pass array into the method, it throws an error when it tries to print. What cause's the method to treat it differently then main method?

Answer 1

I see your error now. You are trying to concatenate or add the string and the int, instead of passing the two arguments to the function.

for _, v := range x {
   fmt.Printf("%d" + v); // The error is in this line
}

It should be:

func printArray(x [3]int) {
    for _, v := range x {
       fmt.Printf("%d", v);
    }
}