vars

README

Package vars provides copy functions for variables.

Quick start

go get github.com/gregoryv/vars

Usage

import github.com/gregoryv/vars

var (
    i int
    s string
)

vars.MustCopy(
    &i, 0, 
    &s, "hello",
)

Documentation

Overview

Package vars provides copy functions for variables.

The purpose of this package is to simplify transfer of data from empty interface{} to a typed destination.

Example (CopyVariables)

package main

import (
	"fmt"

	"github.com/gregoryv/vars"
)

func main() {
	var (
		dest int
		val  interface{} = 1
	)

	err := vars.Copy(&dest, val)
	if err != nil {
		fmt.Println(err)
	}
}

Index

• func Copy(pairs ...interface{}) error
• func CopyAll(pairs ...interface{}) error
• func MapCopy(in map[string]interface{}, pairs ...interface{}) error
• func MapCopyAll(in map[string]interface{}, pairs ...interface{}) error
• func SplitErr(in error) []error

Examples

• Package (CopyVariables)
• Copy
• CopyAll
• MapCopy
• MapCopyAll

Functions

func Copy

func Copy(pairs ...interface{}) error

Copy copies pairwise destination, source. Returns error on first error. Panics if pairs is uneven.

Example

package main

import (
	"fmt"

	"github.com/gregoryv/vars"
)

func main() {
	var (
		i int
		s string
	)
	pairs := []interface{}{
		&i, 1, // ok
		&s, "a", // ok
		&i, "b", // bad
		&s, 0, // bad
	}
	err := vars.Copy(pairs...)
	fmt.Println(err)
}

Output:
Copy[5]: not int

func CopyAll

func CopyAll(pairs ...interface{}) error

CopyAll is similar to Copy but does not fail on first error. Returns nil on no errors.

Example

package main

import (
	"fmt"

	"github.com/gregoryv/vars"
)

func main() {
	var (
		i int
		s string
	)
	pairs := []interface{}{
		&i, 1, // ok
		&s, "a", // ok
		&i, "b", // bad
		&s, 0, // bad
	}
	err := vars.CopyAll(pairs...)

	errs := vars.SplitErr(err)
	for _, err := range errs {
		fmt.Println(err)
	}
}

Output:
Copy[5]: not int
Copy[7]: not string

func MapCopy

func MapCopy(in map[string]interface{}, pairs ...interface{}) error

MapCopy copies values from the given map. Pairs argument must be an even list of destination <- key pairs. Missing keys are ignored.

Example

package main

import (
	"fmt"

	"github.com/gregoryv/vars"
)

func main() {
	data := map[string]interface{}{
		"name":   "John Doe",
		"age":    54,
		"weight": 94.5, // kilos
		"alive":  true,
	}

	var (
		name   string
		age    int
		weight float64
		alive  bool
		addr   string
	)
	err := vars.MapCopy(data,
		&name, "name",
		&age, "age",
		&weight, "weight",
		&alive, "alive",
		&addr, "addr", // missing values are ignored
	)
	if err != nil {
		fmt.Println(err)
	}
}

func MapCopyAll

func MapCopyAll(in map[string]interface{}, pairs ...interface{}) error

MapCopyAll copies values from the given map. Pairs argument must be an even list of destination <- key pairs. Missing keys yield an error.

Example

package main

import (
	"fmt"

	"github.com/gregoryv/vars"
)

func main() {
	data := map[string]interface{}{}

	var addr, name string
	err := vars.MapCopyAll(data,
		&addr, "addr",
		&name, "name",
	)
	if err != nil {
		fmt.Println(err)
		// or each error
		for _, err := range vars.SplitErr(err) {
			fmt.Println(err)
		}
	}
}

Output:
missing "addr", missing "name"
missing "addr"
missing "name"

func SplitErr

func SplitErr(in error) []error

SplitErr takes an error produced by CopyAll or MapCopyAll and splits it into multiple errors. Panics if in error is of other origin or nil.