README
¶
Optional
Optional is a tool that generates 'optional' type wrappers around a given type T.
It is also a library that provides optional types for the primitive Go types.
Motivation
Ever had to write a test where you want to assert something only if a value is present?
tests := []struct {
data string
dataPresent bool
} {
{ "YOLO kombucha slow-carb wayfarers fixie", true },
{ "", false },
}
...
if test.dataPresent {
assert.Equal(t, hipsterism, test.data)
}
Now you can simplify all that with optional types:
tests := []struct {
data optional.String
} {
{ optional.NewString("viral narwhal etsy twee VHS") },
{ optional.String{} },
}
}
...
test.data.If(func(s string) {
assert.Equal(t, hipsterism, s)
})
Marshalling/Unmarshalling JSON
Optional types also marshal to/from JSON as you would expect:
Marshalling
func main() {
var value = struct {
Field optional.String `json:"field,omitempty"`
}{
Field: optional.NewString("bar"),
}
out, _ := json.Marshal(value)
fmt.Println(string(out))
// outputs: {"field":"bar"}
}
Unmarshalling
func main() {
var value = &struct {
Field optional.String `json:"field,omitempty"`
}{}
_ = json.Unmarshal([]byte(`{"field":"bar"}`), value)
value.Field.If(func(s string) {
fmt.Println(s)
})
// outputs: bar
}
See example_test.go for more examples.
Inspiration
- Java Optional
- https://github.com/leighmcculloch/go-optional
- https://github.com/golang/go/issues/7054
Tool
Install
go get -u github.com/markphelps/optional/cmd/optional
Usage
Typically this process would be run using go generate, like this:
//go:generate optional -type=Foo
running this command:
optional -type=Foo
in the same directory will create the file optional_foo.go containing a definition of:
type OptionalFoo struct {
...
}
The default type is OptionalT or optionalT (depending on if the type is exported) and output file is optional_t.go. This can be overridden with the -output flag.
Library
- bool
- byte
- complex128
- complex64
- float32
- float64
- int
- int16
- int32
- int64
- int8
- rune
- string
- uint
- uint16
- uint32
- uint64
- uint8
- uintptr
- error
Usage
import (
"fmt"
"github.com/markphelps/optional"
)
s := optional.NewString("foo")
if s.Present() {
value, _ := s.Get()
fmt.Println(value)
}
t := optional.String{}
fmt.Println(t.OrElse("bar"))
See example_test.go and the documentation for more usage.
Contributing
- Fork it
- Create your feature branch (
git checkout -b my-new-feature) - Commit your changes (
git commit -am 'Add some feature') - Push to the branch (
git push origin my-new-feature) - Create a new Pull Request
Documentation
¶
Overview ¶
Example (Get) ¶
package main
import (
"fmt"
"github.com/markphelps/optional"
)
func main() {
values := []optional.String{
optional.NewString("foo"),
optional.NewString(""),
optional.NewString("bar"),
{},
}
for _, v := range values {
if v.Present() {
value, err := v.Get()
if err == nil {
fmt.Println(value)
}
}
}
}
Output: foo bar
Example (If) ¶
package main
import (
"fmt"
"github.com/markphelps/optional"
)
func main() {
values := []optional.String{
optional.NewString("foo"),
optional.NewString(""),
optional.NewString("bar"),
{},
}
for _, v := range values {
v.If(func(s string) {
fmt.Println("present")
})
}
}
Output: present present present
Example (MarshalJSON) ¶
package main
import (
"encoding/json"
"fmt"
"github.com/markphelps/optional"
)
func main() {
type example struct {
Field *optional.String `json:"field,omitempty"`
}
var values = []optional.String{
optional.NewString("foo"),
optional.NewString(""),
optional.NewString("bar"),
}
for _, v := range values {
out, _ := json.Marshal(&example{
Field: &v,
})
fmt.Println(string(out))
}
}
Output: {"field":"foo"} {"field":""} {"field":"bar"}
Example (OrElse) ¶
package main
import (
"fmt"
"github.com/markphelps/optional"
)
func main() {
values := []optional.String{
optional.NewString("foo"),
optional.NewString(""),
optional.NewString("bar"),
{},
}
for _, v := range values {
fmt.Println(v.OrElse("not present"))
}
}
Output: foo bar not present
Example (UnmarshalJSON) ¶
package main
import (
"encoding/json"
"fmt"
"github.com/markphelps/optional"
)
func main() {
var values = []string{
`{"field":"foo"}`,
`{"field":""}`,
`{"field":"bar"}`,
"{}",
}
for _, v := range values {
var o = &struct {
Field optional.String `json:"field,omitempty"`
}{}
if err := json.Unmarshal([]byte(v), o); err != nil {
fmt.Println(err)
}
o.Field.If(func(s string) {
fmt.Println(s)
})
}
}
Output: foo bar
Index ¶
- type Bool
- type Byte
- type Complex128
- func (c Complex128) Get() (complex128, error)
- func (c Complex128) If(fn func(complex128))
- func (c Complex128) MarshalJSON() ([]byte, error)
- func (c Complex128) OrElse(v complex128) complex128
- func (c Complex128) Present() bool
- func (c Complex128) Set(v complex128)
- func (c *Complex128) UnmarshalJSON(data []byte) error
- type Complex64
- func (c Complex64) Get() (complex64, error)
- func (c Complex64) If(fn func(complex64))
- func (c Complex64) MarshalJSON() ([]byte, error)
- func (c Complex64) OrElse(v complex64) complex64
- func (c Complex64) Present() bool
- func (c Complex64) Set(v complex64)
- func (c *Complex64) UnmarshalJSON(data []byte) error
- type Error
- type Float32
- type Float64
- type Int
- type Int16
- type Int32
- type Int64
- type Int8
- type Rune
- type String
- type Uint
- type Uint16
- type Uint32
- type Uint64
- type Uint8
- type Uintptr
Examples ¶
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
This section is empty.
Types ¶
type Bool ¶
type Bool struct {
// contains filtered or unexported fields
}
Bool is an optional bool
func (Bool) MarshalJSON ¶ added in v0.4.0
func (*Bool) UnmarshalJSON ¶ added in v0.4.0
type Byte ¶
type Byte struct {
// contains filtered or unexported fields
}
Byte is an optional byte
func (Byte) MarshalJSON ¶ added in v0.4.0
func (*Byte) UnmarshalJSON ¶ added in v0.4.0
type Complex128 ¶
type Complex128 struct {
// contains filtered or unexported fields
}
Complex128 is an optional complex128
func NewComplex128 ¶ added in v0.3.0
func NewComplex128(v complex128) Complex128
NewComplex128 creates a optional.Complex128 from a complex128
func (Complex128) Get ¶
func (c Complex128) Get() (complex128, error)
Get returns the complex128 value or an error if not present
func (Complex128) If ¶ added in v0.2.0
func (c Complex128) If(fn func(complex128))
If calls the function f with the value if the value is present
func (Complex128) MarshalJSON ¶ added in v0.4.0
func (c Complex128) MarshalJSON() ([]byte, error)
func (Complex128) OrElse ¶
func (c Complex128) OrElse(v complex128) complex128
OrElse returns the complex128 value or a default value if the value is not present
func (Complex128) Present ¶
func (c Complex128) Present() bool
Present returns whether or not the value is present
func (*Complex128) UnmarshalJSON ¶ added in v0.4.0
func (c *Complex128) UnmarshalJSON(data []byte) error
type Complex64 ¶
type Complex64 struct {
// contains filtered or unexported fields
}
Complex64 is an optional complex64
func NewComplex64 ¶ added in v0.3.0
NewComplex64 creates a optional.Complex64 from a complex64
func (Complex64) If ¶ added in v0.2.0
If calls the function f with the value if the value is present
func (Complex64) MarshalJSON ¶ added in v0.4.0
func (Complex64) OrElse ¶
OrElse returns the complex64 value or a default value if the value is not present
func (*Complex64) UnmarshalJSON ¶ added in v0.4.0
type Error ¶
type Error struct {
// contains filtered or unexported fields
}
Error is an optional error
func (Error) MarshalJSON ¶ added in v0.4.0
func (*Error) UnmarshalJSON ¶ added in v0.4.0
type Float32 ¶
type Float32 struct {
// contains filtered or unexported fields
}
Float32 is an optional float32
func NewFloat32 ¶ added in v0.3.0
NewFloat32 creates a optional.Float32 from a float32
func (Float32) MarshalJSON ¶ added in v0.4.0
func (Float32) OrElse ¶
OrElse returns the float32 value or a default value if the value is not present
func (*Float32) UnmarshalJSON ¶ added in v0.4.0
type Float64 ¶
type Float64 struct {
// contains filtered or unexported fields
}
Float64 is an optional float64
func NewFloat64 ¶ added in v0.3.0
NewFloat64 creates a optional.Float64 from a float64
func (Float64) MarshalJSON ¶ added in v0.4.0
func (Float64) OrElse ¶
OrElse returns the float64 value or a default value if the value is not present
func (*Float64) UnmarshalJSON ¶ added in v0.4.0
type Int ¶
type Int struct {
// contains filtered or unexported fields
}
Int is an optional int
func (Int) MarshalJSON ¶ added in v0.4.0
func (*Int) UnmarshalJSON ¶ added in v0.4.0
type Int16 ¶
type Int16 struct {
// contains filtered or unexported fields
}
Int16 is an optional int16
func (Int16) MarshalJSON ¶ added in v0.4.0
func (*Int16) UnmarshalJSON ¶ added in v0.4.0
type Int32 ¶
type Int32 struct {
// contains filtered or unexported fields
}
Int32 is an optional int32
func (Int32) MarshalJSON ¶ added in v0.4.0
func (*Int32) UnmarshalJSON ¶ added in v0.4.0
type Int64 ¶
type Int64 struct {
// contains filtered or unexported fields
}
Int64 is an optional int64
func (Int64) MarshalJSON ¶ added in v0.4.0
func (*Int64) UnmarshalJSON ¶ added in v0.4.0
type Int8 ¶
type Int8 struct {
// contains filtered or unexported fields
}
Int8 is an optional int8
func (Int8) MarshalJSON ¶ added in v0.4.0
func (*Int8) UnmarshalJSON ¶ added in v0.4.0
type Rune ¶
type Rune struct {
// contains filtered or unexported fields
}
Rune is an optional rune
func (Rune) MarshalJSON ¶ added in v0.4.0
func (*Rune) UnmarshalJSON ¶ added in v0.4.0
type String ¶
type String struct {
// contains filtered or unexported fields
}
String is an optional string
func (String) MarshalJSON ¶ added in v0.4.0
func (String) OrElse ¶
OrElse returns the string value or a default value if the value is not present
func (*String) UnmarshalJSON ¶ added in v0.4.0
type Uint ¶
type Uint struct {
// contains filtered or unexported fields
}
Uint is an optional uint
func (Uint) MarshalJSON ¶ added in v0.4.0
func (*Uint) UnmarshalJSON ¶ added in v0.4.0
type Uint16 ¶
type Uint16 struct {
// contains filtered or unexported fields
}
Uint16 is an optional uint16
func (Uint16) MarshalJSON ¶ added in v0.4.0
func (Uint16) OrElse ¶
OrElse returns the uint16 value or a default value if the value is not present
func (*Uint16) UnmarshalJSON ¶ added in v0.4.0
type Uint32 ¶
type Uint32 struct {
// contains filtered or unexported fields
}
Uint32 is an optional uint32
func (Uint32) MarshalJSON ¶ added in v0.4.0
func (Uint32) OrElse ¶
OrElse returns the uint32 value or a default value if the value is not present
func (*Uint32) UnmarshalJSON ¶ added in v0.4.0
type Uint64 ¶
type Uint64 struct {
// contains filtered or unexported fields
}
Uint64 is an optional uint64
func (Uint64) MarshalJSON ¶ added in v0.4.0
func (Uint64) OrElse ¶
OrElse returns the uint64 value or a default value if the value is not present
func (*Uint64) UnmarshalJSON ¶ added in v0.4.0
type Uint8 ¶
type Uint8 struct {
// contains filtered or unexported fields
}
Uint8 is an optional uint8
func (Uint8) MarshalJSON ¶ added in v0.4.0
func (*Uint8) UnmarshalJSON ¶ added in v0.4.0
type Uintptr ¶
type Uintptr struct {
// contains filtered or unexported fields
}
Uintptr is an optional uintptr
func NewUintptr ¶ added in v0.3.0
NewUintptr creates a optional.Uintptr from a uintptr
func (Uintptr) MarshalJSON ¶ added in v0.4.0
func (Uintptr) OrElse ¶
OrElse returns the uintptr value or a default value if the value is not present
func (*Uintptr) UnmarshalJSON ¶ added in v0.4.0
Source Files
¶
Directories
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| Path | Synopsis |
|---|---|
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cmd
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optional
Optional is a tool that generates 'optional' type wrappers around a given type T. Typically this process would be run using go generate, like this: //go:generate optional -type=Foo running this command optional -type=Foo in the same directory will create the file optional_foo.go containing a definition of type OptionalFoo struct { ...
|
Optional is a tool that generates 'optional' type wrappers around a given type T. Typically this process would be run using go generate, like this: //go:generate optional -type=Foo running this command optional -type=Foo in the same directory will create the file optional_foo.go containing a definition of type OptionalFoo struct { ... |