Late last month, Apple (NASDAQ:AAPL) reported its results for the first quarter of its fiscal 2019, and issued its outlook for the second quarter of the year. The company's first-quarter results were a little bit better than expected, with earnings per share (EPS) beating consensus estimates by a penny and revenue beating by $330 million -- although you have to remember that Apple lowered its outlook on Jan. 2, so that was a beat relative to dramatically lower expectations.

The company also told investors to expect sales of between $55 billion and $59 billion for the second quarter of fiscal 2018, with the midpoint of that range, $57 billion, missing analysts' consensus of nearly $59 billion. Despite these results, the stock bounced, which could mean that while Apple missed analyst expectations, retail and institutional investors' expectations were even lower.

A person holding an iPhone while rain falls on their umbrella

Image source: Apple.

While some investors were clearly excited by these results, I'm not. Here's why.

It comes down to the iPhone

Apple has historically generated and continues to generate the bulk of its revenue from sales of the iPhone. That product category saw sales decline 15% year over year in the first quarter of the company's fiscal 2019 and, as analyst Toni Sacconaghi observed during the conference call, the company's revenue guidance for the second quarter of fiscal 2019 suggests a deceleration in iPhone sales.

Apple CFO Luca Maestri explained that in the second quarter of fiscal 2019, the company does have a $1.3 billion currency-related headwind to cope with, but also indicated that "the macroeconomic environment, particularly in emerging markets, will continue to be [a factor]." (Apple partially blamed a weakening macroeconomic environment for the large decline in iPhone revenue.)

Check out the latest Apple earnings call transcript.

Now, there's no denying that Apple's non-iPhone businesses are actually holding up quite well. According to Apple CEO Tim Cook, Apple's non-iPhone business saw a 19% year-over-year boost in the first quarter of fiscal 2019, and Maestri indicated in his response to Sacconaghi that the company "will continue to grow revenue nicely from the rest of the business which is not iPhone."

Nevertheless, it's hard to get comfortable investing in Apple -- even after shares have declined significantly from the peak -- without more concrete indications that the declines that we'll see in Apple's iPhone business in fiscal 2019 won't be as severe in fiscal 2020 (or, in a more optimistic scenario, will reverse).

That being said, the odds look good that Apple's non-iPhone businesses will keep growing and, as a corollary, become larger components of the company's overall business, thereby mitigating the importance of the iPhone business as time wears on. For investors with relatively long investment horizons and a willingness to deal with a potentially range-bound stock in the interim, this could be a compelling investment thesis.

However, other potential investors might be more inclined to watch Apple's business transformation from the sidelines for now. They might jump in when the company either isn't as reliant on the iPhone to support its financial results, or when the rest of the business becomes large enough (and has robust-enough growth prospects) that a relatively weak iPhone business doesn't hinder overall growth for the company.