A powerful language integrated query (LINQ) library for Go.
- Written in vanilla Go!
- Safe for concurrent use
- Complete lazy evaluation with iterator pattern
- Supports arrays, slices, maps, strings, channels and custom collections
(collection needs to implement
Iterable
interface and element -Comparable
interface)
$ go get github.com/ahmetalpbalkan/go-linq
⚠️ ⚠️ go-linq
has recently introduced breaking API changes with v2.0.0. See release notes for details. v2.0.0 comes with a refined interface, dramatically increased performance and memory efficiency, and new features such as lazy evaluation (read more).The old version is still available in
archive/0.9
branch and tagged as0.9
as well. If you are usinggo-linq
, please vendor a copy of it in your source tree to avoid getting broken by upstream changes.
Usage is as easy as chaining methods like:
From(slice)
.Where(predicate)
.Select(selector)
.Union(data)
Example: Find all owners of cars manufactured from 2015
import . "github.com/ahmetalpbalkan/go-linq"
type Car struct {
id, year int
owner, model string
}
owners := []string{}
From(cars).Where(func(c interface{}) bool {
return c.(Car).year >= 2015
}).Select(func(c interface{}) interface{} {
return c.(Car).owner
}).ToSlice(&owners)
Example: Find the author who has written the most books
import . "github.com/ahmetalpbalkan/go-linq"
type Book struct {
id int
title string
authors []string
}
author := From(books).SelectMany( // make a flat array of authors
func(book interface{}) Query {
return From(book.(Book).authors)
}).GroupBy( // group by author
func(author interface{}) interface{} {
return author // author as key
}, func(author interface{}) interface{} {
return author // author as value
}).OrderByDescending( // sort groups by its length
func(group interface{}) interface{} {
return len(group.(Group).Group)
}).Select( // get authors out of groups
func(group interface{}) interface{} {
return group.(Group).Key
}).First() // take the first author
Example: Implement a custom method that leaves only values greater than the specified threshold
type MyQuery Query
func (q MyQuery) GreaterThan(threshold int) Query {
return Query{
Iterate: func() Iterator {
next := q.Iterate()
return func() (item interface{}, ok bool) {
for item, ok = next(); ok; item, ok = next() {
if item.(int) > threshold {
return
}
}
return
}
},
}
}
result := MyQuery(Range(1,10)).GreaterThan(5).Results()
More examples can be found in documentation.
v2.0.0 (2016-09-02)
* IMPORTANT: This release is a BREAKING CHANGE. The old version
is archived at the 'archive/0.9' branch or the 0.9 tags.
* A COMPLETE REWRITE of go-linq with better performance and memory
efficiency. (thanks @kalaninja!)
* API has significantly changed. Most notably:
- linq.T removed in favor of interface{}
- library methods no longer return errors
- PLINQ removed for now (see channels support)
- support for channels, custom collections and comparables
v0.9-rc4
* GroupBy()
v0.9-rc3.2
* bugfix: All() iterating over values instead of indices
v0.9-rc3.1
* bugfix: modifying result slice affects subsequent query methods
v0.9-rc3
* removed FirstOrNil, LastOrNil, ElementAtOrNil methods
v0.9-rc2.5
* slice-accepting methods accept slices of any type with reflections
v0.9-rc2
* parallel linq (plinq) implemented
* Queryable separated into Query & ParallelQuery
* fixed early termination for All
v0.9-rc1
* many linq methods are implemented
* methods have error handling support
* type assertion limitations are unresolved
* travis-ci.org build integrated
* open sourced on github, master & dev branches