upgrade version of an application

i want to know what things need to be do in developing the upgrade version of an application (like bundle version) so that if a user download my upgrade version of my application then it update the old version.

i have develop the upgrade version of my app in old version and just changed its version no. I need that data of my old app remains t开发者_如何转开发here.

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All data in the document directory will not be touch when upgrading. All files in the bundle will be copies from the new version.