iPhone : how to auto connect to a known wifi SSID?

I know it is possible to list the available Wifi networks on iPhone using the CaptiveNetwork API from official Apple SDK.

I was wondering if there is a way to auto connect to a specific SSID programmatically as long as I can find it in the list returned by CaptiveNetwork ?

How do I get my iPhone to automatically connect to someone else's Wi-Fi?

If your device doesn't automatically join a captive Wi-Fi network, follow these steps: Tap Settings > Wi-Fi. Tap next to the network name. Make sure that Auto-Join is on.

Why is my iPhone not automatically connecting to known Wi-Fi?

When Airplane mode is turned on, your device is unable to connect to any network, including WiFi. You could turn the mode on accidentally, too. Toggling off Airplane mode should fix the problem immediately. Just go to Settings and turn Airplane mode off, then try connecting to your WiFi network.

Apple would not like you to do such things. Connecting to Wifi Stations is the responsibility of the user, so don't expect a public API. See e.g. here. Probably the makers of this app also would like to do it automatically.

Peter