github.com/thiagoyeds/go-cloud@v0.26.0/runtimevar/constantvar/example_test.go (about)

     1  // Copyright 2018 The Go Cloud Development Kit Authors
     2  //
     3  // Licensed under the Apache License, Version 2.0 (the "License");
     4  // you may not use this file except in compliance with the License.
     5  // You may obtain a copy of the License at
     6  //
     7  //     https://www.apache.org/licenses/LICENSE-2.0
     8  //
     9  // Unless required by applicable law or agreed to in writing, software
    10  // distributed under the License is distributed on an "AS IS" BASIS,
    11  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    12  // See the License for the specific language governing permissions and
    13  // limitations under the License.
    14  
    15  package constantvar_test
    16  
    17  import (
    18  	"context"
    19  	"errors"
    20  	"fmt"
    21  	"log"
    22  
    23  	"gocloud.dev/runtimevar"
    24  	"gocloud.dev/runtimevar/constantvar"
    25  )
    26  
    27  func ExampleNew() {
    28  	// Construct a *runtimevar.Variable that always returns "hello world".
    29  	v := constantvar.New("hello world")
    30  	defer v.Close()
    31  
    32  	// We can now read the current value of the variable from v.
    33  	snapshot, err := v.Latest(context.Background())
    34  	if err != nil {
    35  		log.Fatal(err)
    36  	}
    37  	fmt.Println(snapshot.Value.(string))
    38  
    39  	// Output:
    40  	// hello world
    41  }
    42  
    43  func ExampleNewBytes() {
    44  	// Construct a *runtimevar.Variable with a []byte.
    45  	v := constantvar.NewBytes([]byte(`hello world`), runtimevar.BytesDecoder)
    46  	defer v.Close()
    47  
    48  	// We can now read the current value of the variable from v.
    49  	snapshot, err := v.Latest(context.Background())
    50  	if err != nil {
    51  		log.Fatal(err)
    52  	}
    53  	fmt.Printf("byte slice of length %d\n", len(snapshot.Value.([]byte)))
    54  
    55  	// Output:
    56  	// byte slice of length 11
    57  }
    58  
    59  func ExampleNewError() {
    60  	// Construct a runtimevar.Variable that always returns errFake.
    61  	var errFake = errors.New("my error")
    62  	v := constantvar.NewError(errFake)
    63  	defer v.Close()
    64  
    65  	// We can now use Watch to read the current value of the variable
    66  	// from v. Note that Latest would block here since it waits for
    67  	// a "good" value, and v will never get one.
    68  	_, err := v.Watch(context.Background())
    69  	if err == nil {
    70  		log.Fatal("Expected an error!")
    71  	}
    72  	fmt.Println(err)
    73  
    74  	// Output:
    75  	// runtimevar (code=Unknown): my error
    76  }
    77  
    78  func Example_openVariableFromURL() {
    79  	// PRAGMA: This example is used on gocloud.dev; PRAGMA comments adjust how it is shown and can be ignored.
    80  	// PRAGMA: On gocloud.dev, add a blank import: _ "gocloud.dev/runtimevar/constantvar"
    81  	// PRAGMA: On gocloud.dev, hide lines until the next blank line.
    82  	ctx := context.Background()
    83  
    84  	// runtimevar.OpenVariable creates a *runtimevar.Variable from a URL.
    85  
    86  	v, err := runtimevar.OpenVariable(ctx, "constant://?val=hello+world&decoder=string")
    87  	if err != nil {
    88  		log.Fatal(err)
    89  	}
    90  	defer v.Close()
    91  	// PRAGMA: On gocloud.dev, hide the rest of the function.
    92  	snapshot, err := v.Latest(ctx)
    93  	if err != nil {
    94  		log.Fatal(err)
    95  	}
    96  	fmt.Println(snapshot.Value.(string))
    97  
    98  	// Output
    99  	// hello world
   100  }