I'm trying to link GA's User ID feature to my iOS app, but this doesn't seem to be working. From the documentation, I enables a User ID capable view (profile). Then, I set the userId field.
My code: AppDelegate.m
id<GAITracker> tracker = [[GAI sharedInstance] defaultTracker];
// You only need to set User ID on a tracker once. By setting it on the tracker, the ID will be
// sent with all subsequent hits.
[tracker set:@"&uid"
value:@"userIDTest"];
// This hit will be sent with the User ID value and be visible in User-ID-enabled views (profiles).
[tracker send:[[GAIDictionaryBuilder createEventWithCategory:@"User Test" // Event category (required)
action:@"User Sign In" // Event action (required)
label:nil // Event label
value:nil] build]]; // Event value
However, in the analytics dashboard:
I can't seem to find one place where I can see the user id.
You cannot see the user id in Google Analytics at all. It's only there to unify data across devices. To view the user id, try adding a custom dimension which also records user id. Then you'll have access to view it in the interface.
More details on adding custom dimensions to send user IDs to Google Analytics.