When using Combines .first(where: ) operator, why is the value that is printed out H, and not O, in my example code? Thank you

Question

I am asking a question regarding Combines .first(where: ) method. When looking at my code, I use Hello World as the reference by which to check if it contains the values emitted by my publisher.

Why is H the first value thats emitted, when in reality O gets printed first?

I hope my question is not confusing. If you read the code it should make much more sense. Thanks!

// 1 Create a publisher that emits four letters.
    let publisher = ["J", "O", "H", "N"].publisher
    
    // 2 Use the first(where:) operator to find the first letter contained in Hello World and then print it out.
    publisher
        .print("publisher")
        .first(where: { "Hello World".contains($0) })
        .sink(receiveValue: { print("First match is \($0)") })
        .store(in: &subscriptions)

And this is what get's printed to the console:

publisher: receive subscription: (["J", "O", "H", "N"]) 
publisher: request unlimited 
publisher: receive value: (J) 
publisher: receive value: (O) 
publisher: receive value: (H) 
publisher: receive cancel First match is H

Shouldn't the first match be O? Since it's hello world? I understand it also contains hello, but o get's emitted before h.

Thanks once more.

Answer 1

This has nothing to do with Combine, so all that scaffolding just boils down to:

print("Hello World".contains("J")) // false
print("Hello World".contains("O")) // false
print("Hello World".contains("H")) // true
print("Hello World".contains("N")) // false

Which just happens because "o" != "O" and "H" == "H". That is, character equality is sensitive to capitalization.