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iOS

Posted by Julien Schmitt
Julien Schmitt
2,334 Points

Conditional binding error?

Hi guys,

I'm working on optionals and I'm encountering the following error: " Initializer for conditional binding must have Optional Type, not "String". 

let mobilePhone = ["Apple": ["iPhone": ["6", "6S", "6S+"]]]

if let smartphone = mobilePhone["Apple"],
let phoneBrand = smartphone["iPhone"],
let phoneModel = phoneBrand[0] {
print(phoneModel)
}

Would be great if someone could help on this one.

Cheers !

3 Answers

Michael Hulet
Michael Hulet
47,913 Points

When you get a value from an array, the resulting value is not an Optional, as it is when getting a value from a dictionary. In other words, you can't get values from an array in an if let statement, unless the value inside the array is an optional. That being the case, the 3rd assignment in your optional assignment chain can't be there, and you have to move it into the if block itself, like this:

if let smartphone = mobilePhone["Apple"], let phoneBrand = smartphone["iPhone"]{
    print(phoneBrand[0]) //phoneBrand[0] is equivalent to phoneModel from your example
}
Julien Schmitt
Julien Schmitt
2,334 Points
Julien Schmitt
Julien Schmitt
2,334 Points

Hi Michael,

Thanks for the answer.

However what I don't understand here is that I copied the exercice we got and just replaced the values with my own ones just to test.

Here was the exercice: 

let movieDictionary = ["Spectre": ["cast": ["Daniel Craig", "Christoph Waltz", "Léa Seydoux", "Ralph Fiennes", "Monica Bellucci", "Naomie Harris"]]]

var leadActor: String = ""

if let movie = movieDictionary["Spectre"],
    let cast = movie["cast"] {
    leadActor = cast[0]
    print(leadActor)
}

Why is it working with the example above? Is it because it's a dictionary? If so, I don't see the differences between the constant movieDictionary and the constant mobilePhone.

Thanks,

Julien

Michael Hulet
Michael Hulet
47,913 Points

It's working there because leadActor is defined outside of the if let chain. You just can't put the declaration of leadActor inside that list of if let declarations, because it is not an Optional

Julien Schmitt
Julien Schmitt
2,334 Points
Julien Schmitt
Julien Schmitt
2,334 Points

I see.

Thanks for the explanations !