HasPrefix, hasSuffix

A string's beginning or end can be tested in many ways. We could loop over characters. We could take a substring.

But for simplicity, we can use the hasPrefix or hasSuffix methods. These are "starts with" and "ends with" methods. They are easy to call and well-tested.

An example

With the hasPrefix and hasSuffix funcs, we test the starts and ends of strings. These return true or false. They tell us whether the characters exist at the specified place.

var test = "one and two"

// Test the string's prefix.
if test.hasPrefix("one") {
    print(true)
}
// Test the suffix.
if test.hasSuffix("two") {
    print(true)
}
// This prefix is not correct.
// ... Use exclamation mark to test for this condition.
if !test.hasPrefix("abc") {
    print(false)
}
true
true
false

Negation

To determine a string does not start or end with another string, we use the exclamation mark. This means "not." An "else if" can also be used.

Some languages require us to develop special methods for testing prefixes and suffixes. The Swift language does not. We use the built-in hasPrefix and hasSuffix.