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Start your free trialChris White
2,308 PointsIs it me or is the unit test? Using `keys.contains`
I'm trying to determine whether my code isn't working the way I expect it to and my understanding is flawed or the unit test/compiler is too inflexible to account for my solution.
I wanted to try to solve this challenge using the keys.contains
method rather than data["someKey"] != nil
since that's what the directions suggest.
Here's the code I wrote:
enum ParserError: Error {
case emptyDictionary
case invalidKey
}
struct Parser {
var data: [String : String?]?
func parse(data dict: [String : String?]) throws {
guard let data = data else {
throw ParserError.emptyDictionary
}
guard data.keys.contains("someKey") else {
throw ParserError.invalidKey
}
}
}
let data: [String : String?]? = ["someKey": nil]
let parser = Parser(data: data)
// NOTE: I'm not including the following in the code challenge, just checking it in Xcode to validate the same output with valid data.
let validData: [String : String?]? = ["someKey": "I'm valid"]
let validParser = Parser(data: validData)
This returns the following if I fully expand it:
["someKey": nil]
(key "someKey", nil)
key "someKey"
nil
["someKey": "I'm valid"]
(key "someKey", value "I'm valid")
key "someKey"
value "I'm valid"
Unfortunately, I get a compiler error from the Treehouse compiler and when I try to preview it it shakes and gives me no feedback.
After searching around I found this in one of the answers:
struct Parser {
var data: [String : String?]?
func parse() throws {
guard data != nil else {
throw ParserError.emptyDictionary
}
guard data?.keys.contains("someKey") == true else {
throw ParserError.invalidKey
}
}
}
This returns:
["someKey": nil]
(key "someKey", nil)
key "someKey"
nil
["someKey": "I'm valid"]
(key "someKey", value "I'm valid")
key "someKey"
value "I'm valid"
Unless I'm missing something, the output of the function is identical and presumably should pass Treehouse's unit tests — especially since my code is closer to the style @pasan seems to favor in the course — so I'm surprised I'm not able to pass the challenge.
I have to admit, I'm still having a hard time fully wrapping my head around optionals.
Chris White
2,308 PointsChris White
2,308 PointsAh, it definitely is different because with my method I have to pass it data and unwrap it but in the second solution I just call the method
Mine:
vs
However, I don't understand why, is this a scope problem?