Generic materialize function with throwable behaviour for throwable initializers #890

iwheelbuy · 2017-09-08T15:49:02Z

Lets say I have some struct and some enum

enum ValueEnum: Int {
    case first = 1
    case second = 2
}

struct MyStruct {
    let valueBool: Bool?
    let valueDouble: [Double]
    let valueEnum: ValueEnum
    let valueInt: Int
    let valueString: String
}

I want to parse the struct from JSON

struct MyStruct {
    let valueBool: Bool?
    let valueDouble: [Double]
    let valueEnum: ValueEnum
    let valueInt: Int
    let valueString: String
    
    init(json: JSON) throws {
        // parse
    }
}

JSON looks this way

let json: JSON = [
    "valueString": "hello",
    "valueDictionary": [
        "valueInt": 100500
    ],
    "valueDouble": [1.1, 2.2, 3.3],
    "valueEnum": 2
]

This is an example how I'd parse it in a pure SwiftyJSON way

init(json: JSON) throws {
    valueBool = json["valueBool"].bool
    if let valueDouble = json["valueDouble"].array {
        self.valueDouble = try valueDouble
            .map({ (json) -> Double in
                if let double = json.double {
                    return double
                } else {
                    throw SwiftyJSONError.someParsingError
                }
            })
    } else {
        throw SwiftyJSONError.someParsingError
    }
    if let value = json["valueEnum"].int {
        if let valueEnum = ValueEnum(rawValue: value) {
            self.valueEnum = valueEnum
        } else {
            throw SwiftyJSONError.someParsingError
        }
    } else {
        throw SwiftyJSONError.someParsingError
    }
    if let valueInt = json["valueDictionary"]["valueInt"].int {
        self.valueInt = valueInt
    } else {
        throw SwiftyJSONError.someParsingError
    }
    if let valueString = json["valueString"].string {
        self.valueString = valueString
    } else {
        throw SwiftyJSONError.someParsingError
    }
}

My pull request allows to do it this way

init(json: JSON) throws {
    valueBool = json["valueBool"].materialize()
    valueDouble = try json["valueDouble"].materialize()
    valueEnum = try json["valueEnum"].materialize()
    valueInt = try json["valueDictionary"]["valueInt"].materialize()
    valueString = try json["valueString"].materialize()
}

My pull request is just a proposal. Please don't merge it. Lets discuss.
Maybe... I'm missing something and there is already some way to conveniently parse and throw errors.

houndci-bot · 2017-09-08T15:49:16Z

Source/SwiftyJSON.swift

+            throw factoryError(file: file, line: line)()
+        }
+    }
+}


File Line Length Violation: File should contain 400 lines or less: currently contains 1546 (file_length)

houndci-bot · 2017-09-08T15:49:16Z

Source/SwiftyJSON.swift

+    func materialize<T>(file: String = #file, line: Int = #line) throws -> T where T: JSONMaterializableType {
+        return try T.implementation(self, factoryError(file: file, line: line))
+    }
+
