filtgen

CLI tool for generating iterators that selects items by their field values.

Quick Start

Install

go install github.com/miyamo2/filtgen@latest

Usage

Step 1: Tag your struct with the filtgen

//go:generate filtgen generate -s $GOFILE
package main

import (
	"time"
)

type Foo struct {
	StringField     string     `filtgen:"*"`
	IntField        int        `filtgen:"*"`
	BoolField       bool       `filtgen:"*"`
	TimeField       time.Time  `filtgen:"*"`
	ErrorField      error      `filtgen:"*"`
}

Step 2: Run filtgen generate

Run with go generate

go generate ./...

Run with filtgen command

filtgen generate -s your_struct.go

Step 3: Use generated iterator

errSomething := errors.New("something")

s := []Foo{
    {StringField: "a", IntField: 1, BoolField: true, TimeField: time.Now()},
    {StringField: "b", IntField: 2, BoolField: false, TimeField: time.Now(), ErrorField: errSomething},
    {StringField: "c", IntField: 3, BoolField: true, TimeField: time.Now().Add(-(time.Hour * 2))},
}

for i, v := range FooSlice(s).StringFieldGe("a") {
    fmt.Printf("%d: %s\n", i, v.StringField)
}
// Output: 0: a
// 1: b
// 2: c

for i, v := range FooSlice(s).IntFieldGt(1) {
    fmt.Printf("%d: %s\n", i, v.StringField)
}
// Output: 1: b
// 2: c

for i, v := range FooSlice(s).BoolFieldEq(true) {
    fmt.Printf("%d: %s\n", i, v.StringField)
}
// Output: 0: a
// 2: c

for i, v := range FooSlice(s).TimeFieldMatches(func(t time.Time) bool { return t.Before(time.Now()) }) {
    fmt.Printf("%d: %s\n", i, v.StringField)
}
// Output: 2: c

for i, v := range FooSlice(s).ErrorFieldIs(errSomething) {
    fmt.Printf("%d: %s\n", i, v.StringField)
}
// Output: 1: b

// with method chaining
for i, v := range FooSlice(s).IntFieldGt(1).StringFieldNe("c") {
    fmt.Printf("%d: %s\n", i, v.StringField)
}
// Output: 1: b

For the actual generated code, see the example.

What codes to be generated?

Types

filtgen generates the following defined-types.

• XxxSlice([]T)

• XxxMap[K](map[K compareble]T)

• XxxSeq[T](iter.Seq[T])

• XxxSeq2[T](iter.Seq2[T, U])

Type name is determined by the struct name; e.g. User -> UserSlice.

To use the generated methods, cast must be performed.

s := []User{
    {Name: "Alice"},
    {Name: "Bob"},
}
for i, v := range UserSlice(s).NameEq("Alice") {
    fmt.Printf("%d: %s\n", i, v.Name)
}

Methods

Following methods are generated by filtgen.

• XxxEq
• XxxNe
• XxxGt
• XxxLt
• XxxGe
• XxxLe
• XxxMatches
• XxxIs
• XxxIsnt

Method name is determined by the field name; e.g. Name -> NameEq.

XxxEq

Selects iterator items whose field values are equal to the specified value.

type User struct {
    Name string `filtgen:"eq"`
}

for i, v := range UserSlice(s).NameEq("Alice") {
    fmt.Printf("%d: %s\n", i, v.Name)
}

XxxNe

Selects iterator items whose field values are not equal to the specified value.

type User struct {
    Name string `filtgen:"ne"`
}

for i, v := range UserSlice(s).NameNe("Alice") {
    fmt.Printf("%d: %s\n", i, v.Name)
}

XxxGt

Selects iterator items whose field values are greater than the specified value.

type User struct {
    Name string `filtgen:"gt"`
}

for i, v := range UserSlice(s).NameGt("Alice") {
    fmt.Printf("%d: %s\n", i, v.Name)
}

XxxLt

Selects iterator items whose field values are less than the specified value.

type User struct {
    Name string `filtgen:"lt"`
}

for i, v := range UserSlice(s).NameLt("Alice") {
    fmt.Printf("%d: %s\n", i, v.Name)
}

XxxGe

Selects iterator items whose field values are greater than or equal to the specified value.

type User struct {
    Name string `filtgen:"ge"`
}

for i, v := range UserSlice(s).NameGe("Alice") {
    fmt.Printf("%d: %s\n", i, v.Name)
}

XxxLe

Selects iterator items whose field values are less than or equal to the specified value.

type User struct {
    Name string `filtgen:"le"`
}

for i, v := range UserSlice(s).NameLe("Alice") {
    fmt.Printf("%d: %s\n", i, v.Name)
}

XxxMatches

Selects iterator items whose field values match the specified function.

type User struct {
    Name string `filtgen:"matches"`
}

for i, v := range UserSlice(s).NameMatches(func(s string) bool { return strings.HasPrefix(s, "A") }) {
    fmt.Printf("%d: %s\n", i, v.Name)
}

XxxIs

Selects iterator items whose field values are equal to the specified error.
Equivalence is determined by errors.Is.

type Transaction struct {
    ID   string `filtgen:"eq"`
    Err  error  `filtgen:"is"`
}

for i, v := range TransactionSlice(s).ErrIs(fmt.Errorf("something")) {
    fmt.Printf("%d: %s\n", i, v.ID)
}

XxxIsnt

Selects iterator items whose field values are not equal to the specified error.
Equivalence is determined by errors.Is.

type Transaction struct {
    ID   string `filtgen:"eq"`
    Err  error  `filtgen:"isnt"`
}

for i, v := range TransactionSlice(s).ErrIsnt(fmt.Errorf("something")) {
    fmt.Printf("%d: %s\n", i, v.ID)
}

List of compatible filters by type

| Type\Filter | XxxEq | XxxNe | XxxGt | XxxLt | XxxGe | XxxLe | XxxMatches | XxxIs | XxxIsnt | |--------------|---------|---------|---------|---------|---------|---------|--------------|---------|-----------| | string | ✅ | ✅ | ✅ | ✅ | ✅ | ✅ | ✅ | ❌ | ❌ | | int | ✅ | ✅ | ✅ | ✅ | ✅ | ✅ | ✅ | ❌ | ❌ | | int8 | ✅ | ✅ | ✅ | ✅ | ✅ | ✅ | ✅ | ❌ | ❌ | | int16 | ✅ | ✅ | ✅ | ✅ | ✅ | ✅ | ✅ | ❌ | ❌ | | int32 | ✅ | ✅ | ✅ | ✅ | ✅ | ✅ | ✅ | ❌ | ❌ | | int64 | ✅ | ✅ | ✅ | ✅ | ✅ | ✅ | ✅ | ❌ | ❌ | | uint | ✅ | ✅ | ✅ | ✅ | ✅ | ✅ | ✅ | ❌ | ❌ | | uint8 | ✅ | ✅ | ✅ | ✅ | ✅ | ✅ | ✅ | ❌ | ❌ | | uint16 | ✅ | ✅ | ✅ | ✅ | ✅ | ✅ | ✅ | ❌ | ❌ | | uint32 | ✅ | ✅ | ✅ | ✅ | ✅ | ✅ | ✅ | ❌ | ❌ | | uint64 | ✅ | ✅ | ✅ | ✅ | ✅ | ✅ | ✅ | ❌ | ❌ | | float32 | ✅ | ✅ | ✅ | ✅ | ✅ | ✅ | ✅ | ❌ | ❌ | | float64 | ✅ | ✅ | ✅ | ✅ | ✅ | ✅ | ✅ | ❌ | ❌ | | complex64 | ❌ | ❌ | ❌ | ❌ | ❌ | ❌ | ✅ | ❌ | ❌ | | complex128 | ❌ | ❌ | ❌ | ❌ | ❌ | ❌ | ✅ | ❌ | ❌ | | byte | ✅ | ✅ | ✅ | ✅ | ✅ | ✅ | ✅ | ❌ | ❌ | | rune | ✅ | ✅ | ✅ | ✅ | ✅ | ✅ | ✅ | ❌ | ❌ | | error | ❌ | ❌ | ❌ | ❌ | ❌ | ❌ | ✅ | ✅ | ✅ | | bool | ✅ | ✅ | ❌ | ❌ | ❌ | ❌ | ✅ | ❌ | ❌ | | other-types | ❌ | ❌ | ❌ | ❌ | ❌ | ❌ | ✅ | ❌ | ❌ |

filtgen tags

The following values can be set in the filtgen tag.
If you want to set multiple values, separate them with ,.

type A struct {
    StringField string `filtgen:"eq,ne"`
}

| Value | Description | |-----------|---------------------------------------------------------------------| | * | Generate all methods supported according to the type of that field. | | eq | Generate XxxEq methods. | | ne | Generate XxxNe methods. | | `g