github.com/thiagoyeds/go-cloud@v0.26.0/runtimevar/example_openvariable_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 runtimevar_test
    16  
    17  import (
    18  	"context"
    19  	"fmt"
    20  	"log"
    21  
    22  	"gocloud.dev/runtimevar"
    23  	_ "gocloud.dev/runtimevar/constantvar"
    24  )
    25  
    26  func Example_openVariableFromURL() {
    27  	// Connect to a Variable using a URL.
    28  	// This example uses "constantvar", an in-memory implementation.
    29  	// We need to add a blank import line to register the constantvar driver's
    30  	// URLOpener, which implements runtimevar.VariableURLOpener:
    31  	// import _ "gocloud.dev/runtimevar/constantvar"
    32  	// constantvar registers for the "constant" scheme.
    33  	// All runtimevar.OpenVariable URLs also work with "runtimevar+" or "runtimevar+variable+" prefixes,
    34  	// e.g., "runtimevar+constant://..." or "runtimevar+variable+constant://...".
    35  	ctx := context.Background()
    36  	v, err := runtimevar.OpenVariable(ctx, "constant://?val=hello+world&decoder=string")
    37  	if err != nil {
    38  		log.Fatal(err)
    39  	}
    40  	defer v.Close()
    41  
    42  	// Now we can use the Variable as normal.
    43  	snapshot, err := v.Latest(ctx)
    44  	if err != nil {
    45  		log.Fatal(err)
    46  	}
    47  	// It's safe to cast the Value to string since we used the string decoder.
    48  	fmt.Printf("%s\n", snapshot.Value.(string))
    49  
    50  	// Output:
    51  	// hello world
    52  }