github.com/axw/juju@v0.0.0-20161005053422-4bd6544d08d4/api/common/watch.go (about)

     1  // Copyright 2014 Canonical Ltd.
     2  // Licensed under the AGPLv3, see LICENCE file for details.
     3  
     4  package common
     5  
     6  import (
     7  	"fmt"
     8  
     9  	"gopkg.in/juju/names.v2"
    10  
    11  	"github.com/juju/juju/api/base"
    12  	apiwatcher "github.com/juju/juju/api/watcher"
    13  	"github.com/juju/juju/apiserver/params"
    14  	"github.com/juju/juju/watcher"
    15  )
    16  
    17  // Watch starts a NotifyWatcher for the entity with the specified tag.
    18  func Watch(facade base.FacadeCaller, tag names.Tag) (watcher.NotifyWatcher, error) {
    19  	var results params.NotifyWatchResults
    20  	args := params.Entities{
    21  		Entities: []params.Entity{{Tag: tag.String()}},
    22  	}
    23  	err := facade.FacadeCall("Watch", args, &results)
    24  	if err != nil {
    25  		return nil, err
    26  	}
    27  	if len(results.Results) != 1 {
    28  		return nil, fmt.Errorf("expected 1 result, got %d", len(results.Results))
    29  	}
    30  	result := results.Results[0]
    31  	if result.Error != nil {
    32  		return nil, result.Error
    33  	}
    34  	return apiwatcher.NewNotifyWatcher(facade.RawAPICaller(), result), nil
    35  }