Add helper methods to CreatableFromJSON extension

Include two new methods in the CreatableFromJSON protocol extension that simplify turning JSON arrays into data model arrays. The methods that previously existed were only really suitable for use when the arrays were inside a JSON dictionary (which helps keep the failable initializers clean and simple). These new methods are useful outside of that context.

This improvement was brought to my attention by Andrew Duncan http://andrewduncan.net/

Author: Josh Smith

json2swift/swift-code-templates.swift

@@ -42,6 +42,12 @@ private let codeTemplateForCreatableWithJSON = [
     "    /// - Returns: `nil` if the JSON array is missing or if there is an invalid/null element in the JSON array.",
     "    static func createRequiredInstances(from json: [String: Any], arrayKey: String) -> [Self]? {",
     "        guard let jsonDictionaries = json[arrayKey] as? [[String: Any]] else { return nil }",
+    "        return createRequiredInstances(from: jsonDictionaries)",
+    "    }",
+    "",
+    "    /// Attempts to produce an array of instances of the conforming type based on an array of JSON dictionaries.",
+    "    /// - Returns: `nil` if there is an invalid/null element in the JSON array.",
+    "    static func createRequiredInstances(from jsonDictionaries: [[String: Any]]) -> [Self]? {",
     "        var array = [Self]()",
     "        for jsonDictionary in jsonDictionaries {",
     "            guard let instance = Self.init(json: jsonDictionary) else { return nil }",
@@ -54,6 +60,12 @@ private let codeTemplateForCreatableWithJSON = [
     "    /// - Returns: `nil` if the JSON array is missing, or an array with `nil` for each invalid/null element in the JSON array.",
     "    static func createOptionalInstances(from json: [String: Any], arrayKey: String) -> [Self?]? {",
     "        guard let array = json[arrayKey] as? [Any] else { return nil }",
+    "        return createOptionalInstances(from: array)",
+    "    }",
+    "",
+    "    /// Attempts to produce an array of instances of the conforming type, or `nil`, based on an array.",
+    "    /// - Returns: An array of instances of the conforming type and `nil` for each invalid/null element in the source array.",
+    "    static func createOptionalInstances(from array: [Any]) -> [Self?] {",
     "        return array.map { item in",
     "            if let jsonDictionary = item as? [String: Any] {",
     "                return Self.init(json: jsonDictionary)",