NFC Tag Writer sample or tutorial for ios?

Update 2019 - NDEF Write available in iOS 13

Apple just announced at WWDC that they are adding NFC witing of NDEF formatted data.

You cannot write to an NFC tag from iOS, only read. In the Core NFC documentation from Apple it's stated you can only read NFC NDEF tags, and only on iPhone 7 and 7 plus devices (assuming 8 and X are also supported)

https://developer.apple.com/documentation/corenfc

The apps you are finding in the App Store require you to use an external Bluetooth NFC reader.

Update iOS 13 -->

It is now possible to use the CoreNFC framework to write to NFC protocol specific tags such as ISO 7816, ISO 15693, FeliCa™, and MIFARE® tags.

See Apple's example: https://developer.apple.com/documentation/corenfc/creating_nfc_tags_from_your_iphone

It happens now! Writing NFC tags on iOS https://developer.apple.com/documentation/corenfc/creating_nfc_tags_from_your_iphone