Apple has provided a powerful api to play audio from text and here are the steps to achieve:
 

1-  Import AVFoundation framework

2- Initialise AVSpeechSynthesizer(as below)

let synthesizer = AVSpeechSynthesizer()

3- Create an instance of AVSpeechUtterance, using this you can set various parameters like voice, language, pitch, delay and rate to text to be spoken.

let utterance = AVSpeechUtterance(string: text to be spoken)

4- Assign speak utterance to synthesise initialzed above.

synthesizer.speakUtterance(utterance)

5- One can use synthesizer object to stop and pause speech using methods provided:
 

func stopSpeakingAtBoundary(boundary: AVSpeechBoundary) -> Bool
func pauseSpeakingAtBoundary(boundary: AVSpeechBoundary) -> Bool

above AVSpeechBoundary is speech constraint which describse when speech is to be paused or stopped.

Sample Code (In Swift)

let synthesizer = AVSpeechSynthesizer()
            	let utterance = AVSpeechUtterance(string: text to be spoken)
            	utterance.rate = 0.5
           	 utterance.voice = AVSpeechSynthesisVoice(language: "fr-FR")
           	 synthesizer.speakUtterance(utterance)