Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

iOS

Tuan Do
Tuan Do
3,495 Points
Posted by Tuan Do
Tuan Do
3,495 Points

Optional binding chaining

What's the difference between the two code snippets below or are they equivalent?

if let currentWeather = forecast?.currentWeather {
}

and

if let weatherForecast = forecast, let currentWeather = weatherForecast.currentWeather {
}

1 Answer

Jhoan Arango
Jhoan Arango
14,575 Points
Jhoan Arango
Jhoan Arango
14,575 Points

Hello:

Yes, they are equivalent, it's just that one is shorter than the other. 

/* 
This one is going straight to the currentWeather,
by calling forecast?.currentWeather. This will return current weather
*/

if let currentWeather = forecast?.currentWeather {
}

and 

/*
This one is doing a second step by first getting forecast 
and assigning it to weatherForecast, and then we get
currentWeather with the dot notation. "weatherForecast.currentWeather"
*/

if let weatherForecast = forecast, let currentWeather = weatherForecast.currentWeather {
}

Anything you don't understand, let me know and I can clarify it better.

Good luck

Tuan Do
Tuan Do
3,495 Points
Tuan Do
Tuan Do
3,495 Points

That makes sense. Thanks!