Question 121154 in Redis Question posted in
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go-redis Eval func return value type, when Lua script returns an array

When a Lua script returns a table array during an Eval call, how can it be converted to a []string in go?

The redis cli returns bulk replies in the following format.

1) val1
2) val2

Will go-redis eval function return the bulk entries as

["val1", "val2"]
Tags:

2

Answers


  1. 0

    You can use the encoding/json package to convert a JSON string to a slice of strings.

    package main

import (
    "encoding/json"
    "fmt"
)

// jsonString is the JSON string that you want to convert to a slice of strings.
const jsonString = `["value1", "value2"]`

func main() {
   
    var stringSlice []string

    // Unmarshal the JSON string into the stringSlice variable.
    err := json.Unmarshal([]byte(jsonString), &stringSlice)
    if err != nil {
        fmt.Println(err)
        return
    }

    
    fmt.Println(stringSlice) // ["value1", "value2"]
}
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  2. 0

    Redis returns Lua table arrays as RESP2 arrays. The Go client then will map that response to Go native types. The relevant documentation for go-redis is found here: Lua and Go types.

    The tl;dr is that Lua tables are indeed mapped to a bulk reply, and the Go client maps that to a slice of interface: []interface{}.

    Both go-redis script Run and Eval return a *Cmd. You can use methods on this type to retrieve the output as Go types. Result gives (interface{}, error), which you can type-assert to whatever you want, otherwise, StringSlice is a convenience getter to retrieve []string right away.

    So it looks like:

    script := redis.NewScript(`
  local foo = {"val1", "val2"}
  return foo
`)

cmd := script.Run(/* parameters */)

i, err := cmd.Result() // (interface, error)
// or
ss, err := cmd.StringSlice() // ([]string, error)

    If the values aren’t actually all strings, use Slice to get the []interface{} slice, and then inspect the elements individually.

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