Implementing dynamic strings in golang - string

Question

I have following global string,
studentName := "Hi ? ,Welcome"
Now I want to take this string dynamically
func returnName(name string) string{
return studentName+name
}
This function should return string as
Hi name,welcome.
string should take name from parameter,and return dynamic string.What is the best way to implement this in golang.

Answer 1

If you want to keep things simple, you can probably just use fmt.Sprintf.
studentName := fmt.Sprintf("Hi, %s! Welcome.", name)
The %s part will get replaced by the value of name.

Answer 2

If your input gets bigger (more complex) or if you need to substitute different values multiple times, then templates are more effective, cleaner and more flexible. Check out the text/template package.
The template package parses your template once, builts a tree from it, and once you need to replace values, it builds the output on the fly.
Take a look at this example:
const templ = `Hi {{.Name}}!
Welcome {{.Place}}.
Please bring {{.ToBring}}
`
You can parse such a template with this line:
t := template.Must(template.New("").Parse(templ))
Prepare its input data either as a struct or as a map:
data := map[string]string{
"Name": "Bob",
"Place": "Home",
"ToBring": "some beers",
}
And you can have the result with Template.Execute():
err := t.Execute(os.Stdout, data) // Prints result to the standard output
Here's the complete, runnable example: (try it on the Go Playground)
package main
import (
"os"
"text/template"
)
func main() {
data := map[string]string{
"Name": "Bob",
"Place": "Home",
"ToBring": "some beers",
}
t := template.Must(template.New("").Parse(templ))
if err := t.Execute(os.Stdout, data); err != nil { // Prints result to the standard output
panic(err)
}
// Now change something:
data["Name"] = "Alice"
data["ToBring"] = "a Teddy Bear"
if err := t.Execute(os.Stdout, data); err != nil {
panic(err)
}
}
const templ = `
Hi {{.Name}}!
Welcome {{.Place}}.
Please bring {{.ToBring}}
`
Output:
Hi Bob!
Welcome Home.
Please bring some beers
Hi Alice!
Welcome Home.
Please bring a Teddy Bear
Getting the result as a string:
If you want the result as a string, you can write the result to a bytes.Buffer and get the string using the Buffer.String() method:
buf := bytes.Buffer{}
t.Execute(&buf, data)
var result string = buf.String()
Complete program (try it on the Go Playground):
package main
import (
"bytes"
"fmt"
"text/template"
)
func main() {
data := map[string]string{
"Name": "Bob",
"Place": "Home",
"ToBring": "some beers",
}
fmt.Print(Execute(data))
}
var t = template.Must(template.New("").Parse(templ))
func Execute(data interface{}) string {
buf := bytes.Buffer{}
if err := t.Execute(&buf, data); err != nil {
fmt.Println("Error:", err)
}
return buf.String()
}
const templ = `
Hi {{.Name}}!
Welcome {{.Place}}.
Please bring {{.ToBring}}
`

Answer 3

You could consider the function strings.Replace
return Replace(studentName, "? ", name, 1)
With '1', it replaces the first "? " it finds in studentName.
Replace returns a copy of studentName, with "? " substituted with name.
This strictly respect the original question (global var with that exact content)
Now, if you start changing the question, like for instance with a different content (a global variable studentName := "Hi %s ,Welcome"), then you could use fmt.Sprintf() as in 425nesp's answer
return fmt.Sprintf(studentName, name)
That would use the format 'verbs' %s, default format for string.

Answer 4

Assuming the global string is always the same you could do.
func returnName(name string) string {
buf := bytes.Buffer{}
buf.WriteString("Hi ")
buf.WriteString(name)
buf.WriteString(", welcome")
return buf.String()
}
or
func returnName(name string) string {
return "Hi " + name + ", welcome"
}
if the string is a dynamic template you could use the template package or a simple Replace if there wont be other ? marks or Sprintf

Answer 5

You can also use template.Template
combined with strings.Builder:
package main
import (
"strings"
"text/template"
)
func returnName(name string) string {
t, b := new(template.Template), new(strings.Builder)
template.Must(t.Parse("Hi {{.}}, welcome.")).Execute(b, name)
return b.String()
}
func main() {
println(returnName("Akash"))
}