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golang builder pattern
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| package main | |
| // tip of the hat to Jon Calhoun | |
| // | |
| // see also: https://www.calhoun.io/using-functional-options-instead-of-method-chaining-in-go/ | |
| import ( | |
| "errors" | |
| "fmt" | |
| "strings" | |
| ) | |
| type FakeBuilder struct { | |
| Result string | |
| err error | |
| } | |
| func wrap(s string) string { | |
| return "<" + strings.TrimSpace(s) + ">" | |
| } | |
| func (f *FakeBuilder) Append(val string) *FakeBuilder { | |
| if f.err != nil { | |
| return f | |
| } | |
| if val == "error" { | |
| f.err = errors.New("invalid value") | |
| } | |
| f.Result = f.Result + wrap(val) | |
| return f | |
| } | |
| func (f *FakeBuilder) Prepend(val string) *FakeBuilder { | |
| if f.err != nil { | |
| return f | |
| } | |
| f.Result = wrap(val) + f.Result | |
| return f | |
| } | |
| func (f *FakeBuilder) Err() error { | |
| return f.err | |
| } | |
| func main() { | |
| var fb FakeBuilder | |
| err := fb.Append(" hi ").Prepend("2021-09-23: ").Prepend(" does it do anything ").Append(" more ").Err() | |
| if err != nil { | |
| panic(err) | |
| } | |
| fmt.Println(fb.Result) | |
| var fb2 FakeBuilder | |
| err = fb2.Append("hi").Prepend("2021-09-23: ").Append("error").Prepend("does it do anything").Err() | |
| if err != nil { | |
| panic(err) | |
| } | |
| fmt.Println(fb2.Result) | |
| } |
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