Golang : cannot assign type int to value (type uint8) in range error



Tags : golang cannot-assign-type error

Sometimes, we tend to overlook a small part of for--loop just because we use it frequently and expect the compiler or linker to alert us of the problem before run time. The problem described below is only visible during run time :

Problem :

You get an error message that look like this :

cannot assign type int to value (type uint8) in range

or something similar when trying to use range. For example :

 package main

 import "fmt"

 func main() {
 var xs []uint8 = []uint8{123, 124, 125}

 var value uint8
 for value = range xs {
 fmt.Println(value)
 }
 }

Solution :

That is because, range over a slice or array will return 2 values.... but yet the code will compile will issue! To fix this error. Change the codes to :

 package main

 import "fmt"

 func main() {
 var xs []uint8 = []uint8{123, 124, 125}
 var value uint8
 for _, value = range xs { // ignore the key
 fmt.Println(value)
 }
 }

or

 package main

 import "fmt"

 func main() {
 var xs []uint8 = []uint8{123, 124, 125}
 var key uint8
 var value uint8
 for key, value = range xs { // assign the key to a variable. 
 fmt.Println(key, value)
 }
 }

output :

0 123

1 124

2 125



Tags : golang cannot-assign-type error

By Adam Ng

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