Direct from Apple's commentary relating to their slashing Q1 revenue guidance (bolding mine):

  • While we anticipated some challenges in key emerging markets, we did not foresee the magnitude of the economic deceleration, particularly in Greater China. In fact, most of our revenue shortfall to our guidance, and over 100 percent of our year-over-year worldwide revenue decline, occurred in Greater China across iPhone, Mac and iPad.
  • China's economy began to slow in the second half of 2018. The government-reported GDP growth during the September quarter was the second lowest in the last 25 years. We believe the economic environment in China has been further impacted by rising trade tensions with the United States. As the climate of mounting uncertainty weighed on financial markets, the effects appeared to reach consumers as well, with traffic to our retail stores and our channel partners in China declining as the quarter progressed. And market data has shown that the contraction in Greater China's smartphone market has been particularly sharp.

AUD is down, as you'd expect. With a bid for yen also AUD/JPY a big loser:

more to come

Looking further ahead says Apple:

  • Despite these challenges, we believe that our business in China has a bright future. The iOS developer community in China is among the most innovative, creative and vibrant in the world. Our products enjoy a strong following among customers, with a very high level of engagement and satisfaction. Our results in China include a new record for Services revenue, and our installed base of devices grew over the last year. We are proud to participate in the Chinese marketplace.

That's nice but forex markets tend to take a more short-term view for the immediate swings. if you a long term investor yeah, ignore the wobbles. but if you are a leveraged trader this sort of news impacts (as you can see).