fix mixin

Author: Jeff Dickey

src/commands/duration.js

@@ -1,16 +1,18 @@
 // @flow
 
 import Command from 'cli-engine-command'
-import Duration from '../mixins/duration'
+import Duration, {DurationFlag} from '../mixins/duration'
 
 export default class extends Command {
   static topic = 'cli'
   static command = 'duration'
   static description = 'this is an example command showing duration parsing'
+  static flags = [DurationFlag]
 
   duration = new Duration(this)
 
   run () {
-    this.log(`duration: ${this.duration.toString()}`)
+    this.log('duration:')
+    this.inspect(this.duration.value)
   }
 }

src/mixins/duration.js

@@ -2,7 +2,7 @@
 
 import type Command from 'cli-engine-command'
 
-export const FLAG = {
+export const DurationFlag = {
   name: 'duration',
   description: 'a duration',
   required: true,
@@ -15,7 +15,7 @@ export default class Duration {
     this.cmd = cmd
   }
 
-  get duration (): Date {
+  get value (): Date {
     let duration = this.cmd.flags.duration
     return new Date(duration)
   }