On 22/12/15 23:47, jamie hu wrote: > Thanks for the reply Alan. If init code calls launch method then I > would have problems in looking up objects afterwards.
In that case use the init to do the config then explicitly call the launch. > For example: > 1. First or initial calls to VirtualMachine(memory, vcpu, network, > base_image) will try to launch a VM and return a vmid string. > 2. Now if I need to terminate all VMs with a specific base_image then > I will use VirtualMachine.find_by_baseimage() method. This needs to > return VirtualMachine objects with matching base image. This is the same as your previous question, so I'd store the VMs in a dictionary keyed by vmid. I'd put the dictionary in the class (not the instance) as an attribute. And i'd make the find method a class method. > 3. If this data was stored in a database then, before returning this > data I will need to call init method again. Yes, but would you really be running so many virtual machines that you'd store it in a database? Maybe if you run a very large data center you would but that seems an unlikely use for a database. But if you wanted to and didn't want to start an identical VM then you definitely need to keep the init for config and have a separate launch() method. See previous mails for how to instantiate an existing object from the database. > As init is calling launch method, wouldn't this trigger VM launch again? > Or am I missing something here? No, it's just that you've now included several extra requirements that weren't in the original spec. The requirements largely determine the design. -- Alan G Author of the Learn to Program web site http://www.alan-g.me.uk/ http://www.amazon.com/author/alan_gauld Follow my photo-blog on Flickr at: http://www.flickr.com/photos/alangauldphotos _______________________________________________ Tutor maillist - Tutor@python.org To unsubscribe or change subscription options: https://mail.python.org/mailman/listinfo/tutor
