Swift Sort List True Before False

In Swift, sorting an array is a common operation, and there are various ways to achieve this. However, what if you want to sort a list of elements representing boolean values, where true values should come before false values? This is a special case that requires a custom sorting function that takes into account the boolean values.

Example

Suppose you have an array of boolean values like this:

let nums = [true, false, false, true, true, false]

If you simply sort this array using the built-in sort() function, it will sort the elements in ascending order as follows:

let sortedNums = nums.sorted()
// Output: [false, false, false, true, true, true]

As you can see, the false values come before the true values. However, if you want to sort the list so that true values come before false values, you need to define a custom sorting function.

Defining a Custom Sorting Function

To sort a list so that true values come before false values, you can define a custom sorting function that takes into account the boolean values. Here's an example:

let sortedNums = nums.sorted { $0 && !$1 }
// Output: [true, true, true, false, false, false]

This custom sorting function uses the logical AND and NOT operators to compare each pair of boolean values. It returns true if the first value is true and the second value is false, and false otherwise. When you pass this function to the sorted() method, it will sort the elements as desired.

Conclusion

Sorting a list of boolean values so that true values come before false values requires a custom sorting function that takes into account the boolean values. By using the logical AND and NOT operators, you can compare each pair of boolean values and sort them accordingly.