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GoFlagBuilder

GoFlagBuilder provides simple tools to construct command line flags and a file parser to manipulate a given structure. It uses reflection to traverse a potentially hierarchical object of structs and maps and install handlers in Go's standard flag package. Constructed parsers scan given documents line by line and apply key/value pairs found.

Constructed flags have the form Foo=..., Bar=..., Obj.Field=... and so on. Maps and exposed fields of structs with primitive types are consumed, so in this case Foo and Bar might be map keys or public struct fields to a primitive. Nested maps and structs are followed, producing dot-notation hierarchical keys such as Obj.Field.

Primitive types understood by GoFlagBuilder include bool, float64, int64, int, string, uint64, and uint. Slices of these primitive types are supported as well.

Primitive fields in the given object and sub-objects must be settable. In general this means structs should be passed in as pointers. Maps may also be set directly.

Build Status GoDoc Go Report Card

Example

A very simple example:

package main

import (
	"flag"
	"log"

	"github.com/BellerophonMobile/goflagbuilder/v2"
)

type server struct {
	Domain string
	Port   int
}

func Example_Simple() {

	myserver := &server{}

	// Construct the flags
	if err := From(myserver); err != nil {
		log.Fatal("Error: " + err.Error())
	}

	// Read from the command line to establish the param
	flag.Parse()

}

This would establish the command line flags "-Port" and "-Domain".

A more elaborate example including nested structures and using the parser is available here. There are also a series of tests in the package outlining exactly what input structures are valid.

Changelog

  • 2018/10/15: v2.1.0 Clean up path from FlagSet name for environment variable parsing.
  • 2018/10/03: v2.0.3 Ignore unexported fields of structs.
  • 2018/10/03: v2.0.2 Fix crash when printing values.
  • 2018/10/03: v2.0.1 Remove mistakenly included logging, and formatting.
  • 2018/08/16: v2.0.0 Simplified package a bit, split config file parsing to its own sub-package. Added a new sub-package to read environment variables.
  • 2014/11/03: v1.0.0 Though not mature at all, we consider GoFlagBuilder to be usable.

License

GoFlagBuilder is provided under the open source MIT license:

The MIT License (MIT)

Copyright (c) 2018 Bellerophon Mobile

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.