Read Space Seperated Strings in Golang 1.8

Question

Hi I have two problems in the following Go Program .
1. I couldn't read the space seperated string using Scanf or Scanln.
So I have added a formatted string "%q" to read space seperated string using double quotes. Is there an alternative to read string with spaces ?

package main
import
(
    "fmt"
    "strings"
)

type details struct{
    DataType string
    Table string

}
func main(){
    dt := details{}
    fmt.Println("Enter the DataType")
    fmt.Scanf("%q" ,&dt.DataType )
    for strings.TrimSpace(dt.DataType) == "" {
        fmt.Println("Enter the DataType")
        fmt.Scanln(&dt.DataType)
    }
    //fmt.Println(dt.DataType)
    fmt.Println("Enter the Table")
    fmt.Scanln(&dt.Table)
    for strings.TrimSpace(dt.Table) == "" {
        fmt.Println("Enter a valid Table name ")
        fmt.Scanln(&dt.Table)
    }
}

The Console output is as follows ,

VenKats-MacBook-Air:ColumnCreator venkat$ go run test.go
Enter the DataType
"rid bigint not null"
Enter the Table
Enter a valid Table name

The Second problem is why does the control flow went to the second for loop without waiting for the user input . Does the Scanf with "%q" returned a carraige return . Any help would be greatly appreciated

Reading an line from input is somewhat non-intuitive in Go, it seems that lot of beginners stumble on that one. See this question for an example how to do it: http://stackoverflow.com/q/20895552/723693 — ain, Feb 19 '17 at 08:15
Interesting that entering `data type` and `"data type"` has one carriage return less than or more than necessary! :\ — Kaveh Shahbazian, Feb 20 '17 at 15:58

score 1 · Accepted Answer · answered Feb 21 '17 at 06:19

Perhaps something like this..

package main

import (
    "bufio"
    "fmt"
    "os"
    "strings"
)

type details struct {
    DataType string
    Table    string
}

func main() {
    dt := details{}
    cin := bufio.NewReader(os.Stdin)
    for {
        fmt.Println("Enter the DataType")
        text, err := cin.ReadString('\n') // reads entire string up until the /n which is the newline deliminator
        if strings.TrimSpace(text) == "" { // check to see if the input is empty
            continue
        }
        if err == nil { // if the input is not empty then the control got this far and now we just have to check for error, assign the data, and break out of the loop .. repeat for the second input. If this is going to be something you do alot refactor the input section.
            dt.DataType = text
            break
        } else {
            fmt.Printf("An error as occured: %s\n", err.Error())
        }
    }
    for {
        fmt.Println("Enter the Table")
        text, err := cin.ReadString('\n')
        if strings.TrimSpace(text) == "" {
            continue
        }
        if err == nil {
            dt.Table = text
            break
        } else {
            fmt.Printf("An error as occured: %s\n", err.Error())
        }
    }
    fmt.Printf("%+v\n", dt)
    return
}

Example of refactored code:

package main

import (
    "bufio"
    "fmt"
    "os"
    "strings"
)

type details struct {
    DataType string
    Table    string
}

func getInput(message string, reader bufio.Reader) (input string) {
    for {
        fmt.Println(message)
        input, err := reader.ReadString('\n')
        if strings.TrimSpace(input) == "" {
            continue
        }
        if err == nil {
            break
        } else {
            fmt.Printf("An error as occured: %s\n", err.Error())
        }
    }
    return
}

func main() {
    dt := details{}
    cin := bufio.NewReader(os.Stdin)
    t := getInput("Enter the DataType", *cin)
    dt.DataType = t
    t = getInput("Enter the Table", *cin)
    dt.Table = t
    fmt.Printf("Seeing what my data looks like  %+v\n", dt)
    return
}

Read Space Seperated Strings in Golang 1.8

1 Answers1