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