Check out the optional.go file for more details on the usage.
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Go: Optional parameters
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| package main | |
| import ( | |
| "example/optional" | |
| "fmt" | |
| ) | |
| func main() { | |
| say("world") | |
| say("hello", SayArgs{withExclamationMark: optional.Arg(true)}) | |
| } | |
| type SayArgs struct { | |
| milliseconds *optional.ArgType[int] | |
| withExclamationMark *optional.ArgType[bool] | |
| } | |
| func say(s string, args ...SayArgs) { | |
| opts := optional.GetOpts(&args) | |
| milliseconds := optional.Get(opts.milliseconds, 100) | |
| withExclamationMark := optional.Get(opts.withExclamationMark, false) | |
| if withExclamationMark { | |
| s = fmt.Sprint(s, "!") | |
| } | |
| fmt.Println(s) | |
| } |
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| // Package optional deals with cases where you would like to have optional arguments for a function. | |
| package optional | |
| // ArgType is used to define optional arguments of a function. | |
| // Typically, the type function will have the optional arguments | |
| // that are defined as a struct, placed as a last argument(s) of the function. | |
| // An example: | |
| // | |
| // type MyFunctionArgs struct { | |
| // someInt *optional.ArgType[int] | |
| // someBool *optional.ArgType[bool] | |
| // } | |
| // | |
| // func MyFunction(someRequiredString string, args ...MyFunctionArgs) {} | |
| type ArgType[T any] struct { | |
| Value T | |
| } | |
| // Arg is used in function calls to pass optional arguments. | |
| // It returns a pointer to an ArgType that is expected by the function with optional arguments. | |
| // | |
| // If the function uses a struct to hold the optional arguments | |
| // you could pass them and use optional.Arg(value) to pass a different | |
| // value for the function instead of the default one. | |
| // | |
| // Here's an example: | |
| // MyFunction("some required string", MyFunctionArgs{someBool: optional.Arg(true)}) | |
| // | |
| // There is no need to provide the generic type, as it can be inferred | |
| // from the value you pass as an argument to this function. | |
| func Arg[T any](Value T) *ArgType[T] { | |
| return &ArgType[T]{Value} | |
| } | |
| // GetOpts transforms the slice argument of the variadic function (taking only | |
| // the first item from the slice) into a single args struct instance. | |
| // If the slice is empty, then an empty struct instance will be returned. | |
| // | |
| // An example of the usage inside a function: | |
| // | |
| // func MyFunction(someRequiredString string, args ...MyFunctionArgs) { | |
| // opts := optional.GetOpts(&args) | |
| // } | |
| func GetOpts[T any](opts *[]T) *T { | |
| if len(*opts) > 0 { | |
| return &(*opts)[0] | |
| } | |
| var empty T | |
| return &empty | |
| } | |
| // Get returns a default value or the one from the option if it's not nil. | |
| // Here is a full example of a function that has its optional arguments | |
| // defined as a struct and how the default values are provided. | |
| // | |
| // type MyFunctionArgs struct { | |
| // someInt *optional.ArgType[int] | |
| // someBool *optional.ArgType[bool] | |
| // } | |
| // | |
| // func MyFunction(someRequiredString string, args ...MyFunctionArgs) { | |
| // opts := optional.GetOpts(&args) | |
| // someInt := optional.Get(opts.someInt, 100) | |
| // someBool := optional.Get(opts.someBool, false) | |
| // } | |
| // | |
| // There is no need to provide the generic type, as it can be inferred | |
| // from the option (from the struct) and from the type of the defaultValue. | |
| func Get[T any](option *ArgType[T], defaultValue T) T { | |
| if option != nil { | |
| return option.Value | |
| } | |
| return defaultValue | |
| } |
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