eival

eival is a Go utility package for converting your interface{} to your desired basic type through automatic type assertion against all its compatible types and conversion when necessary.

For example, retrieving a float64:

• from a string will use strconv.ParseFloat()
• from a int will convert it directly
• from a bool will return 1.0 or 0.0
• from a date will return strconv
• from a map[string]interface{} will fail

Usage

package main

import (
    ev "github.com/rgzr/eival"
    "time"
    "fmt"
)

func main() {
    var m = map[string]interface{}{
        "a": time.Now(),
        "b": "123",
        "c": "myNumber",
        "d": "myOtherNumber",

    }

    // The StringZ(), IntZ()... functions return the value on success.
    fmt.Println(ev.StringZ(123)+"!!") // prints "123!!"
    fmt.Println(ev.StringZ(m["a"])) // prints "2009-11-10T23:00:00Z"
    fmt.Println(ev.IntZ(m["b"])) // prints "123"
    // They return the zero value when conversion is not possible.
    fmt.Println(ev.IntZ(m["c"])) // prints 0
    
    // The String(), Int()... functions return the value and a boolean to check if the conversion failed
    number, ok := ev.Int(m["d"])
    if !ok {
        fmt.Println("not yet") // will print "not yet"
    }
    fmt.Println(number) // will print the zero value

    // The MapZI(), SliceZI()... functions (only available to a few types, like slices or maps) return an initialized, zero-length object if the conversion fails or the underlying object was nil.
    var myNilMap map[string]interface{}
    fmt.Println(ev.MapZI(myNilMap) == nil) // will print false 
}

Notes

Greatly inspired by github.com/jaracil/ei but taking a different approach.

For a full list of the possible conversions, take a look at the source code, as it's almost self-explanatory.