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package survey
import (
"reflect"
"strings"
"golang.org/x/text/cases"
"golang.org/x/text/language"
)
// TransformString returns a `Transformer` based on the "f"
// function which accepts a string representation of the answer
// and returns a new one, transformed, answer.
// Take for example the functions inside the std `strings` package,
// they can be converted to a compatible `Transformer` by using this function,
// i.e: `TransformString(strings.Title)`, `TransformString(strings.ToUpper)`.
//
// Note that `TransformString` is just a helper, `Transformer` can be used
// to transform any type of answer.
func TransformString(f func(s string) string) Transformer {
return func(ans interface{}) interface{} {
// if the answer value passed in is the zero value of the appropriate type
if isZero(reflect.ValueOf(ans)) {
// skip this `Transformer` by returning a zero value of string.
// The original answer will be not affected,
// see survey.go#L125.
// A zero value of string should be returned to be handled by
// next Transformer in a composed Tranformer,
// see tranform.go#L75
return ""
}
// "ans" is never nil here, so we don't have to check that
// see survey.go#L338 for more.
// Make sure that the the answer's value was a typeof string.
s, ok := ans.(string)
if !ok {
return ""
}
return f(s)
}
}
// ToLower is a `Transformer`.
// It receives an answer value
// and returns a copy of the "ans"
// with all Unicode letters mapped to their lower case.
//
// Note that if "ans" is not a string then it will
// return a nil value, meaning that the above answer
// will not be affected by this call at all.
func ToLower(ans interface{}) interface{} {
transformer := TransformString(strings.ToLower)
return transformer(ans)
}
// Title is a `Transformer`.
// It receives an answer value
// and returns a copy of the "ans"
// with all Unicode letters that begin words
// mapped to their title case.
//
// Note that if "ans" is not a string then it will
// return a nil value, meaning that the above answer
// will not be affected by this call at all.
func Title(ans interface{}) interface{} {
transformer := TransformString(cases.Title(language.English).String)
return transformer(ans)
}
// ComposeTransformers is a variadic function used to create one transformer from many.
func ComposeTransformers(transformers ...Transformer) Transformer {
// return a transformer that calls each one sequentially
return func(ans interface{}) interface{} {
// execute each transformer
for _, t := range transformers {
ans = t(ans)
}
return ans
}
}
|
