Sync (button) on Iphone Application

Can anyone tell me How does the Sync Button on many Iphone app. works (like 'Le Monde'). The button download and replace all files of the application? only look for change (new entry) on the database and add them?....

Thanks开发者_如何学运维,

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Typically a button like that is making a web service call, depending on the call you may be updating or replacing the information currently on the device.

Some web services will allow you to ask for information since a certain date:

/FetchArticles?afterDate=200911011952

Some will just provide you with a set amount of information.

Most of the time the calls to a web service will return light enough data that you can just replace what you had with what you fetch, but sometimes the data is a little heavier(images, video, etc...), so you'll want to hang onto what you already have and add to it.

Without knowing more about your App, or if it even uses network resources it's hard to provide any more help.