Prefer Swift's for-in loop over traditional C for loop

I'm sure most of us started our first programming adventures in C.

How many times have you written

for (int i = 0; i < blah; i++)

or something similar in countless methods, functions, etc.?

In C, C++, Javascript, Java, it's ubiquitous.

Then I came upon the most glorious programming language ever created, Ruby

for index in 0..5
    puts "Value of local variable is #{i}"
end

This is obviously equivalent to:

for (int index = 0; i <= 5; i++)

The ease of reading should be obvious in Ruby's typical verbosity. Not that any programmer worth his/her salt can't immediately decipher a traditional for loop.

The idea though is to flow code in a way we read natural language.

So it was no suprise that Swift adopted this for-in loop pattern, and in all cases you should prefer to use this format over the C for loop.

Here's Swift's for-in

for index in 0...5 {
    print("current index is \(index)")
}

Now notice something slightly different

.. vs. ...

In Ruby .. means inclusive (in the example above 0 to 5 including 5). If you added one more dot, ... you'd get exclusive, meaning 0 to 5 excluding 5 (0,1,2,3,4).

In Swift, not the case, ... means inclusive. There currently isn't an exclusive dot offering, although when Swift was first released I remember there being 2 options. This makes sense, in reality if you need exclusive use, you juse use 1 less in value for your range maximum.

You even have the option to just exclude the variable name if it's not needed.

for _ in 0...5 {
    print("Hello")
}

Just remember, that will print 6 not 5 times. A better visualization when you want to do something a set number of times would be to start with 1, 1...5 (visualize needing to do something 5 times).

A good example that I'm currently using that to me reads better is parsring rows and columns in an app:

for rowIndex in 0...self.rows {
    for columnIndex in 0...self.columns {
        // now you have each row and column index.            
    }
}

Having said that there are without a doubt instances where you need to use a C for loop.

Swift's is slightly different:

for var index = 0; index < 10; index += 2 {
    print("index is \(index)")
}

Imagine you need to increment by 2, or multiply by 2 each time, or decrease in value, etc.