How do I update submodule?

My file gitmodules is

[submodule "RestKit"]
    path = RestKit
    url = git://github.com/RestKit/RestKit.git
[submodule "rest开发者_如何转开发kit"]
    path = restkit
    url = git://github.com/RestKit/RestKit.git`enter code here`

My project is :

How do I update submodule?

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Not sure how to do this in XCode but you can do it in the terminal with

git submodule foreach \
git pull origin master

This will loop through all your submodules and do a git pull on them.