Looks like there are some underground compiler settings changes in XCode 5.1.

So to fix this issue you need add -w flag to ZXingWidget Other Warning Flags. This flag completely disable all compiler warnings.

Select ZXingWidget framework.
Select ZXingWidget target in ZXingWidget framework.
Press Build setting tab and type "other wa" in search.
Add -w parameter flag to Other Warning Flags.
Here is a screen with steps how to add this flag:


http://stackoverflow.com/questions/22411565/build-error-on-ios-7-1-zxing