@@ -0,0 +1,120 @@
+import UIKit
+
+struct MultipartFormData {
+    private(set) var boundary: String
+    let contentType: String
+    private(set) var body: Data = Data()
+    
+    init(uuid: String = UUID().uuidString) {
+        self.boundary = "Boundary-\(uuid)"
+        self.contentType = "multipart/form-data; boundary=\(self.boundary)"
+    }
+    
+    mutating func appendToBody(from data: Data) {
+        self.body.append(data)
+    }
+    
+    func createFormData<Item: Codable>(params: String, item: Item) -> Data {
+        var data = Data()
+        data.append(BoundaryGenerator.boundaryData(forBoundaryType: .startSymbol, boundary: boundary))
+        data.append(ContentDisposition.formData(params: params).bodyComponent)
+        
+        let encodedResult = JSONParser<Item>().encode(from: item)
+        switch encodedResult {
+        case .success(let encodedData):
+            data.append(encodedData)
+        case .failure(let error):
+            print(error.localizedDescription)
+        }
+        data.append(BoundaryGenerator.boundaryData(forBoundaryType: .endSymbol, boundary: boundary))
+        
+        return data
+    }
+    
+    func createImageFormData(name: String, fileName: String, contentType: ImageContentType, image: UIImage) -> Data {
+        var data = Data()
+        data.append(BoundaryGenerator.boundaryData(forBoundaryType: .startSymbol, boundary: boundary))
+        data.append(ContentDisposition.imageFormData(name: name, filename: fileName).bodyComponent)
+        data.append(ContentDisposition.imageContentType(type: contentType).bodyComponent)
+        
+        switch contentType {
+        case .png:
+            if let imageData = image.pngData() {
+                data.append(imageData)
+            }
+        case .jpeg:
+            if let imageData = image.jpegData(compressionQuality: 1) {
+                data.append(imageData)
+            }
+        }
+        data.append(BoundaryGenerator.boundaryData(forBoundaryType: .endSymbol, boundary: boundary))
+        
+        return data
+    }
+    
+    mutating func closeBody() {
+        self.body.append(BoundaryGenerator.boundaryData(forBoundaryType: .terminator, boundary: boundary))
+    }
+}
+
+enum ImageContentType: String, CustomStringConvertible {
+    case png
+    case jpeg
+    
+    var description: String {
+        return "image/\(rawValue)"
+    }
+}
+
+enum ContentDisposition {
+    case formData(params: String)
+    case imageFormData(name: String, filename: String)
+    case imageContentType(type: ImageContentType)
+    
+    var bodyComponent: String {
+        switch self {
+        case .formData(let params):
+            return "Content-Disposition: form-data; name=\"\(params)\""
+                    + EncodingCharacters.doubleNewLine
+        case .imageFormData(let name, let filename):
+            return "Content-Disposition: form-data; name=\"\(name)\"; filename=\"\(filename)\""
+                    + EncodingCharacters.newLine
+        case .imageContentType(let type):
+            return "Content-Type: \(type.description)" + EncodingCharacters.doubleNewLine
+        }
+    }
+}
+
+enum EncodingCharacters {
+    static let newLine = "\r\n"
+    static let doubleNewLine = "\r\n\r\n"
+}
+
+enum BoundaryGenerator {
+    enum BoundaryType {
+        case startSymbol, endSymbol, terminator
+    }
+    
+    static func boundaryData(forBoundaryType boundaryType: BoundaryType, boundary: String) -> Data {
+        let boundaryText: String
+        
+        switch boundaryType {
+        case .startSymbol:
+            boundaryText = "--\(boundary)\(EncodingCharacters.newLine)"
+        case .endSymbol:
+            boundaryText = "\(EncodingCharacters.newLine)"
+        case .terminator:
+            boundaryText = "--\(boundary)--"
+        }
+        
+        return Data(boundaryText.utf8)
+    }
+}
+
+private extension Data {
+    mutating func append(_ string: String?) {
+        if let stringData = string?.data(using: .utf8) {
+            self.append(stringData)
+        }
+    }
+}

리뷰: Type 이름에 'XXFormData'가 포함되어있으므로, method 이름에 FormData가 포함되지 않는 것이 호출했을 때 자연스럽습니다.
multipartFormdata.create만 해도 맥락을 이해하는데 문제 없어요.

또한 item이라는 파라미터 이름이 모호해보입니다. 정확히 저게 무슨 item인지 더 자세하게 명세되었으면 합니다.