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

     1  // Copyright 2019 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 blobvar_test
    16  
    17  import (
    18  	"context"
    19  	"fmt"
    20  	"log"
    21  
    22  	"gocloud.dev/blob/memblob"
    23  	"gocloud.dev/runtimevar"
    24  	"gocloud.dev/runtimevar/blobvar"
    25  )
    26  
    27  func ExampleOpenVariable() {
    28  	// Create a *blob.Bucket.
    29  	// Here, we use an in-memory implementation and write a sample value.
    30  	bucket := memblob.OpenBucket(nil)
    31  	defer bucket.Close()
    32  	ctx := context.Background()
    33  	err := bucket.WriteAll(ctx, "cfg-variable-name", []byte("hello world"), nil)
    34  	if err != nil {
    35  		log.Fatal(err)
    36  	}
    37  
    38  	// Construct a *runtimevar.Variable that watches the blob.
    39  	v, err := blobvar.OpenVariable(bucket, "cfg-variable-name", runtimevar.StringDecoder, nil)
    40  	if err != nil {
    41  		log.Fatal(err)
    42  	}
    43  	defer v.Close()
    44  
    45  	// We can now read the current value of the variable from v.
    46  	snapshot, err := v.Latest(ctx)
    47  	if err != nil {
    48  		log.Fatal(err)
    49  	}
    50  	// runtimevar.Snapshot.Value is decoded to a string.
    51  	fmt.Println(snapshot.Value.(string))
    52  
    53  	// Output:
    54  	// hello world
    55  }
    56  
    57  func Example_openVariableFromURL() {
    58  	// PRAGMA: This example is used on gocloud.dev; PRAGMA comments adjust how it is shown and can be ignored.
    59  	// PRAGMA: On gocloud.dev, add a blank import: _ "gocloud.dev/runtimevar/blobvar"
    60  	// PRAGMA: On gocloud.dev, hide lines until the next blank line.
    61  	ctx := context.Background()
    62  
    63  	// runtimevar.OpenVariable creates a *runtimevar.Variable from a URL.
    64  	// The default opener opens a blob.Bucket via a URL, based on the environment
    65  	// variable BLOBVAR_BUCKET_URL.
    66  
    67  	v, err := runtimevar.OpenVariable(ctx, "blob://myvar.txt?decoder=string")
    68  	if err != nil {
    69  		log.Fatal(err)
    70  	}
    71  	defer v.Close()
    72  }