I’m at the end of the chapter and Listing 5.12 is:
let age = 25
if case 18...35 = age {
print("Cool demographic")
}
I feel the syntax is inconsistent because we are using “=” instead of “==” Is there some sort of value binding going on or pattern matching that I don’t get?
If I fiddle with Listing 5.13 (with multiple conditions) and change the “>=” to “=” I get an error:
if case 18...35 = age, age >= 25 {print ("text...")} // -> fiddling works
if case 18...35 = age, age = 25 {print ("text...")} // -> doesn't work
if case 18...35 = age, age == 25 {print ("text...")} // -> fiddling further works
in the second condition I have to use “==”
this works: if case age = 25, age == 25 {print("text...") }
but this doesn’t: if case age == 25, age == 25 {print("text..") } // doesn't work
So my question is, why is the first condition different from the rest, that I have to use “=” instead of “==” to check the condition is true?
It is just syntax; you just need to get used to it
In the context of an if statement, you can think of case 18…35 = age as being the same as the boolean expression age >= 18 && age <=35; and case 25 = age as being the same as age == 25.
Note, however that neither case 18…32 = age nor case 25 = age are boolean expressions.
// The following if statements have the same effect.
if case 18...35 = age {
print ("age is in 18...35")
}
if age >= 18 && age <= 35 {
print ("age is in 18...35")
}
The above if case statement can also be written like this:
let between_18_and_35 = {(v:Int) -> Bool in
switch v {
case 18...25:
return true
default:
return false
}
}
if between_18_and_35 (age) {
print ("age is in 18...35")
}
