├── .gitignore ├── LICENSE ├── README.md └── optional ├── optional.go └── optional_test.go /.gitignore: -------------------------------------------------------------------------------- 1 | .idea 2 | goptional.iml -------------------------------------------------------------------------------- /LICENSE: -------------------------------------------------------------------------------- 1 | Apache License 2 | Version 2.0, January 2004 3 | http://www.apache.org/licenses/ 4 | 5 | TERMS AND CONDITIONS FOR USE, REPRODUCTION, AND DISTRIBUTION 6 | 7 | 1. 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We also recommend that a 185 | file or class name and description of purpose be included on the 186 | same "printed page" as the copyright notice for easier 187 | identification within third-party archives. 188 | 189 | Copyright {yyyy} {name of copyright owner} 190 | 191 | Licensed under the Apache License, Version 2.0 (the "License"); 192 | you may not use this file except in compliance with the License. 193 | You may obtain a copy of the License at 194 | 195 | http://www.apache.org/licenses/LICENSE-2.0 196 | 197 | Unless required by applicable law or agreed to in writing, software 198 | distributed under the License is distributed on an "AS IS" BASIS, 199 | WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 200 | See the License for the specific language governing permissions and 201 | limitations under the License. 202 | -------------------------------------------------------------------------------- /README.md: -------------------------------------------------------------------------------- 1 | [![Go Report Card](https://goreportcard.com/badge/gojp/goreportcard)](https://goreportcard.com/report/gojp/goreportcard) 2 | 3 | goptional is a lightweight library to provide a container for optional values in golang. 4 | 5 | ## Initialization 6 | 7 | ```go 8 | // Create an optional with an initial value 9 | opt, _ := optional.Of(5) 10 | 11 | // An optional created with a nil value returns an error 12 | _, err := optional.Of(nil) 13 | 14 | // Create an empty optional 15 | opt := optional.OfEmpty() 16 | ``` 17 | 18 | ### Nil pointer 19 | 20 | ```go 21 | var nilPointer *int 22 | _, err := Of(nilPointer) // err is not nil 23 | ``` 24 | 25 | ### Nil array 26 | 27 | ```go 28 | nilArray := [3]int{} 29 | _, err := Of(nilArray) // err is not nil 30 | ``` 31 | 32 | ### Nil slice 33 | 34 | ```go 35 | var nilSlice []int 36 | _, err := Of(nilSlice) // err is not nil 37 | ``` 38 | 39 | ### Nil map 40 | 41 | ```go 42 | var nilMap map[int]int 43 | _, err := Of(nilMap) // err is not nil 44 | ``` 45 | 46 | ### Nil function 47 | 48 | ```go 49 | var nilFunction func() 50 | _, err := Of(nilFunction) // err is not nil 51 | ``` 52 | 53 | ### Nil structure 54 | 55 | ```go 56 | type Point struct { 57 | x, y int 58 | } 59 | var emptyPoint Point 60 | _, err = Of(emptyPoint) // err is nil 61 | ``` 62 | 63 | ## Features 64 | 65 | ```go 66 | // Get its value and an eventual error if the optional is empty 67 | v, err := opt.Get() 68 | 69 | // Get the optional value regardless of its emptiness 70 | v := opt.GetValue() 71 | 72 | // Test if the optional is not empty 73 | opt.IsPresent() 74 | 75 | // Execute a function if the optional is not empty 76 | opt.IfPresent(f) 77 | 78 | // Execute a function if the optional is empty 79 | opt.IfNotPresent(f) 80 | 81 | // Returns an error if the optional is not empty (otherwise returns a nil value) 82 | err := opt.IfPresentError(errors.New("present") 83 | 84 | // Returns an error if the optional is empty (otherwise returns a nil value) 85 | err := opt.IfNotPresentError(errors.New("not present") 86 | 87 | // Panic if the optional is not empty 88 | opt.IfPresentPanic("present") 89 | 90 | // Panic if the optional is empty 91 | opt.IfNotPresentPanic("not present") 92 | ``` -------------------------------------------------------------------------------- /optional/optional.go: -------------------------------------------------------------------------------- 1 | /* 2 | A container for optional values. 3 | */ 4 | 5 | package optional 6 | 7 | import ( 8 | "errors" 9 | "reflect" 10 | ) 11 | 12 | type optional struct { 13 | v interface{} 14 | empty bool 15 | } 16 | 17 | // Test if an input is the default zero value 18 | func isZeroed(in interface{}, t reflect.Type) bool { 19 | return in == reflect.Zero(t).Interface() 20 | } 21 | 22 | // Test if nil depending on its type 23 | func isNil(in interface{}) bool { 24 | if in == nil { 25 | return true 26 | } 27 | 28 | t := reflect.TypeOf(in) 29 | 30 | switch t.Kind() { 31 | case reflect.Ptr, reflect.Array: 32 | if isZeroed(in, t) { 33 | return true 34 | } 35 | case reflect.Slice, reflect.Func, reflect.Map: 36 | value := reflect.ValueOf(in) 37 | 38 | if value.IsNil() { 39 | return true 40 | } 41 | case reflect.Struct: 42 | return false 43 | } 44 | 45 | return false 46 | } 47 | 48 | // Create an optional with an initial value 49 | func Of(in interface{}) (optional, error) { 50 | if isNil(in) { 51 | return optional{nil, true}, errors.New("input shall not be nil") 52 | } 53 | 54 | return optional{in, false}, nil 55 | } 56 | 57 | // Create an empty optional 58 | func OfEmpty() optional { 59 | o := optional{nil, true} 60 | 61 | return o 62 | } 63 | 64 | // Get the optional value with an eventual error if the optional is empty 65 | func (v *optional) Get() (interface{}, error) { 66 | if v.IsPresent() { 67 | return v.v, nil 68 | } 69 | 70 | return nil, errors.New("optional is empty") 71 | } 72 | 73 | // Get the optional value regardless of its emptiness 74 | func (v *optional) GetValue() interface{} { 75 | return v.v 76 | } 77 | 78 | // Test whether the optional is not empty 79 | func (v *optional) IsPresent() bool { 80 | return !v.empty 81 | } 82 | 83 | // If the optional is not empty, execute a function taking the optional value as the input parameter 84 | func (v *optional) IfPresent(f func(interface{})) { 85 | if v.IsPresent() { 86 | f(v.v) 87 | } 88 | } 89 | 90 | // If the optional is empty, execute a function 91 | func (v *optional) IfNotPresent(f func()) { 92 | if !v.IsPresent() { 93 | f() 94 | } 95 | } 96 | 97 | // If the optional is not empty, returns an error. Otherwise, returns a nil value 98 | func (v *optional) IfPresentError(e error) error { 99 | if v.IsPresent() { 100 | return e 101 | } 102 | 103 | return nil 104 | } 105 | 106 | // If the optional is empty, returns an error. Otherwise, returns a nil value 107 | func (v *optional) IfNotPresentError(e error) error { 108 | if !v.IsPresent() { 109 | return e 110 | } 111 | 112 | return nil 113 | } 114 | 115 | // If the optional is not empty, panic 116 | func (v *optional) IfPresentPanic(i interface{}) { 117 | if v.IsPresent() { 118 | panic(i) 119 | } 120 | } 121 | 122 | // If the optional is empty, panic 123 | func (v *optional) IfNotPresentPanic(i interface{}) { 124 | if !v.IsPresent() { 125 | panic(i) 126 | } 127 | } 128 | -------------------------------------------------------------------------------- /optional/optional_test.go: -------------------------------------------------------------------------------- 1 | package optional 2 | 3 | import ( 4 | "errors" 5 | "testing" 6 | ) 7 | 8 | type point struct { 9 | x, y int 10 | } 11 | 12 | type complexPoint struct { 13 | time int 14 | p point 15 | } 16 | 17 | func TestOfWithNilValue(t *testing.T) { 18 | _, err := Of(nil) 19 | 20 | if err == nil { 21 | t.FailNow() 22 | } 23 | 24 | _, err = Of(5) 25 | 26 | if err != nil { 27 | t.FailNow() 28 | } 29 | } 30 | 31 | func TestNilPointer(t *testing.T) { 32 | var p *int 33 | 34 | _, err := Of(p) 35 | 36 | if err == nil { 37 | t.FailNow() 38 | } 39 | } 40 | 41 | func TestArray(t *testing.T) { 42 | array := [...]int{1, 2, 3} 43 | nilArray := [3]int{} 44 | 45 | _, err := Of(array) 46 | 47 | if err != nil { 48 | t.FailNow() 49 | } 50 | 51 | _, err = Of(nilArray) 52 | 53 | if err == nil { 54 | t.FailNow() 55 | } 56 | } 57 | 58 | func TestMap(t *testing.T) { 59 | m := map[int]int{3: 2} 60 | var nilMap map[int]int 61 | 62 | _, err := Of(m) 63 | 64 | if err != nil { 65 | t.FailNow() 66 | } 67 | 68 | _, err = Of(nilMap) 69 | 70 | if err == nil { 71 | t.FailNow() 72 | } 73 | } 74 | 75 | func TestSlice(t *testing.T) { 76 | slice := []int{1, 2, 3} 77 | var nilSlice []int 78 | 79 | _, err := Of(slice) 80 | 81 | if err != nil { 82 | t.FailNow() 83 | } 84 | 85 | _, err = Of(nilSlice) 86 | 87 | if err == nil { 88 | t.FailNow() 89 | } 90 | 91 | _, err = Of([]int(nil)) 92 | 93 | if err == nil { 94 | t.FailNow() 95 | } 96 | } 97 | 98 | func TestStruct(t *testing.T) { 99 | var p point 100 | var c complexPoint 101 | var nilStructPointer *point 102 | 103 | _, err := Of(p) 104 | 105 | if err != nil { 106 | t.FailNow() 107 | } 108 | 109 | _, err = Of(c) 110 | 111 | if err != nil { 112 | t.FailNow() 113 | } 114 | 115 | _, err = Of(point{3, 2}) 116 | 117 | if err != nil { 118 | t.FailNow() 119 | } 120 | 121 | _, err = Of(complexPoint{0, point{}}) 122 | 123 | if err != nil { 124 | t.FailNow() 125 | } 126 | 127 | _, err = Of(nilStructPointer) 128 | 129 | if err == nil { 130 | t.FailNow() 131 | } 132 | } 133 | 134 | func TestFunction(t *testing.T) { 135 | var f func() 136 | 137 | _, err := Of(f) 138 | 139 | if err == nil { 140 | t.FailNow() 141 | } 142 | } 143 | 144 | func TestIsPresent(t *testing.T) { 145 | a, _ := Of(5) 146 | b := OfEmpty() 147 | 148 | if !a.IsPresent() { 149 | t.FailNow() 150 | } 151 | 152 | if b.IsPresent() { 153 | t.FailNow() 154 | } 155 | } 156 | 157 | func TestGet(t *testing.T) { 158 | a, _ := Of(5) 159 | b := OfEmpty() 160 | 161 | v, err := a.Get() 162 | 163 | if v != 5 || err != nil { 164 | t.FailNow() 165 | } 166 | 167 | v, err = b.Get() 168 | 169 | if v != nil || err == nil { 170 | t.FailNow() 171 | } 172 | } 173 | 174 | func TestIfPresentError(t *testing.T) { 175 | a, _ := Of(5) 176 | b := OfEmpty() 177 | 178 | if a.IfPresentError(errors.New("")) == nil { 179 | t.FailNow() 180 | } 181 | 182 | if b.IfPresentError(errors.New("")) != nil { 183 | t.FailNow() 184 | } 185 | } 186 | 187 | func TestIfNotPresentError(t *testing.T) { 188 | a, _ := Of(5) 189 | b := OfEmpty() 190 | 191 | if a.IfPresentError(errors.New("")) == nil { 192 | t.FailNow() 193 | } 194 | 195 | if b.IfPresentError(errors.New("")) != nil { 196 | t.FailNow() 197 | } 198 | } 199 | 200 | func TestIfPresent(t *testing.T) { 201 | a := OfEmpty() 202 | 203 | a.IfPresent(fError1) 204 | a.IfPresentPanic("test fails") 205 | } 206 | 207 | func TestIfNotPresent(t *testing.T) { 208 | a, _ := Of(5) 209 | 210 | a.IfNotPresent(fError2) 211 | a.IfNotPresentPanic("test fails") 212 | } 213 | 214 | func fError1(i interface{}) { 215 | panic("test fails") 216 | } 217 | 218 | func fError2() { 219 | panic("test fails") 220 | } 221 | --------------------------------------------------------------------------------