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example_test.go
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63 lines (52 loc) · 1.69 KB
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// Copyright © 2019 The Things Network Foundation, The Things Industries B.V.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package log
import (
"fmt"
"strings"
)
func ExampleMiddleware() {
// build our custom handler (needed for example tests, because it expects us to use fmt.Println)
handler := HandlerFunc(func(entry Entry) error {
fmt.Printf("%s: %s\n", strings.ToUpper(entry.Level().String()), entry.Message())
return nil
})
logger := NewLogger(WithHandler(handler), WithLevel(InfoLevel))
// printer is a middleware that prints the strings be
printer := MiddlewareFunc(func(next Handler) Handler {
return HandlerFunc(func(entry Entry) error {
fmt.Println("== Before ==")
err := next.HandleLog(entry)
fmt.Println("== After ==")
return err
})
})
messages := 0
// counter is a middleware that counts the messages
counter := MiddlewareFunc(func(next Handler) Handler {
return HandlerFunc(func(entry Entry) error {
messages++
return next.HandleLog(entry)
})
})
logger.Use(printer)
logger.Use(counter)
logger.Info("Hey!")
fmt.Println("Number of messages:", messages)
// Output:
// == Before ==
// INFO: Hey!
// == After ==
// Number of messages: 1
}