Swift compiler segmentation fault when building

Question

Adding a (convenient) computed height property to UIView in my UIViewExtension.swift file is causing the Swift compiler to segfault...

Answer 1

This typically happens when the compiler does not have enough information (despite what you think) to guarantee/determine the state of a statement or a variable within a statement.

For example, imagine you have a dictionary of type [String: String] which you populate with city names as keys and a comma separated list of corresponding zip codes/post codes.

Imagine that somewhere in your code you want to update the list of corresponding codes:

myDict[town] += newZipCode + ","

In this case, the compiler will respond with segmentation fault as town might not be in the dictionary and therefore it cannot guarantee that the above statement will have a valid value.

To resolve this, you should store the current state of myDict[town] in a separate variable allowing you to handle the case of key not in dict and then update the value for the given key:

myDict[town] = guaranteedValue + "," newZipCode + ","

Unfortunately, it is not always straightforward to determine the root cause so I hope this simple example helps.