GoogleTagManager error: _avn has no backing implementation

问题

This simple push to the data layer of a screen view prints an error with verbose logging enabled. This and subsequent calls to the data layer all fail. They are neither logged nor executed.

[[TAGManager instance].dataLayer push:@{@"event" : @"screen-loads",
                                                    @"screen-name": [tracker get:kGAIScreenName],
                                                    @"viewController" :NSStringFromClass([sender class])
                                                    }];

This is the error message being logged:

GoogleTagManager error: _avn has no backing implementation.

回答1:

The clue was in _avn. Our friends over at Analytics Pros took a look at the container and noticed that we had a reference to the built in variable {{App Version Name}}. They noticed that wasn't set, and they think it's a variable that is no longer part of v2.

Anyway, changing {{App Version Name}} to {{App Version Code}} got rid of the error and data is flowing freely. Hope this helps.

来源：https://stackoverflow.com/questions/31041263/googletagmanager-error-avn-has-no-backing-implementation