In Swift How do I iterate over an array getting 2 variables when each pair of elements is a String? and a String - swift

Question

I want to iterate over an array String?, String repeated pair but I cannot form the "for case let (a,b) in array" correctly.
The best I have come up with is to create a temp struct of {String?, String} and create an array of the temp structs and then iterate it but I would like to skip this step.
Below is the basic example with the last for loop showing the error Xcode reports.
class Foo {
var s1: String?
var s2: String?
var s3: String?
}
let foo = Foo()
foo.s1="Test1"
foo.s2=nil
foo.s3="Test3"
let fooArray = [foo.s1, ", ", foo.s2, "; ", foo.s3,"."]
let fooArray1 = [foo.s1,foo.s2, foo.s3]
var text:String = ""
for case let prop? in fooArray1 {
text = text + prop + " / "
}
print(text)
// The above works but now I want to use a different separator
//base on the property name
text=""
for case let (prop, sep) in fooArray { // Error <= Expression Type
// [String?] is ambiguous without more context
text = text + prop + sep
}
print(text)
Here is what I have come up with
struct temp {
var prop:String?
var sep:String
init(_ prop:String?, _ sep:String) {
self.prop=prop
self.sep=sep
}
let ary:[temp] = [ temp(foo.s1,", "), temp(foo.s2,"; "), temp(foo.s3,".") ]
text = ""
for a in ary {
if let p = a.prop {
text = text + p + a.sep
}
}
print (text)
is there another way just using the for loop
for (a,b) in fooArray {
...
}

Answer 1

As noted by #RJE, the inferred type of fooArray, as defined in your code, is [String?].
Here is one way to make it work:
class Foo {
var s1: String?
var s2: String?
var s3: String?
}
let foo = Foo()
foo.s1 = "Test1"
foo.s2 = nil
foo.s3 = "Test3"
let fooArray1 = [foo.s1, foo.s2, foo.s3]
let separators = [", ", "; ", "."]
var text = ""
for i in fooArray1.indices {
if let p = fooArray1[i] {
text = text + p + separators[i]
}
}
print (text) //Test1, Test3.
Or
let zipped = zip(fooArray1, separators)
let text = zipped.map { tuple -> String in
if case let (x?, y) = tuple {
return x + y
} else {
return ""
}
}.joined()
print (text) //Test1,Test3.
Or
let fooArray = [foo.s1, ", ", foo.s2, "; ", foo.s3, "."]
var text = ""
var step = 1
var index = 0
while index < fooArray.count {
if let str = fooArray[index] {
step = 1
text += str
} else {
step = 2
}
index += step
}
print(text) //Test1, Test3.
It would be better to define the initializer this way :
class Foo {
var s1: String?
var s2: String?
var s3: String?
init(s1: String?, s2: String?, s3: String?) {
self.s1 = s1
self.s2 = s2
self.s3 = s3
}
}
let foo = Foo(s1: "Test1", s2: nil, s3: "Test3")
P.S: The desired output seems to be more appropriate for a description property of the Foo class.

Answer 2

Thanks for the answer I was hoping through this question to get a better understanding of how to use [for] parameters. But the while solution is the solution I would probably use with the following modifications
text = ""
var index = 0
while index < fooArray.count {
if let prop = fooArray[index] {
index += 1
let sep = fooArray[index]!
index += 1
text = text + prop + sep
} else {
index += 2
}
}