if let: How not to use it
Table of Contents
Today I want to show you how you should write a code in a way that shows your true intention. I use my old code that misuse if let
as an example.
When I wrote this, only God and I understood what I was doing.
Now, only God knows.
Problem
I got an optional object with an optional property.
struct User {
let name: String
let address: Address?
}
let user: User? = User(name: "John", address: nil)
There is a time when I need to check for the presence of an object property to treat it differently.
Without much thought, sometimes, my muscle memory will write something like this.
if let user = user, let address = user.address {
// Some logic that use `user`, but not `address`
}
I'm in a hurry, so I ignore the Xcode warning. Many months passed by coming back to refactor my code, and I see this warning.
I follow the solution and remove it.
if let user = user {
// Some logic that use `user`, but not `address`
}
A few minutes later, my CI failed. My UI tests failing, and I spent minutes fixing them.
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What my past self should do
Instead of abusive use of let address = user.address
, I should write in a way that expresses the real intent.
... to check for the presence of an object property ...
I should write it like this.
if let user = user, user.address != nil {
// Some logic that use `user`, but not `address`
}
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Conclusion
By using language features correctly, you do colleagues and your future self a favor. A little bit of thought at a very early stage can save you significant time in the future.
Read more article about Swift, Semantic, or see all available topic
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