New documentations are added

Author: burak.uzunboy

README.md

@@ -9,3 +9,161 @@
 From Xcode simply select `File > Swift Packages > Add Package Dependency...` and paste `https://github.com/exozet/iOSUsefulNetworkLayer` to search field. You can specify rules according to your preferences and you are ready to use. 
 
 
+## Usage
+
+### Creating a response object
+
+NetworkLayer needs an object which is inherited from `ResponseBodyParsable` class in order to create responses. There is two `required` initializer from that object, whether from the `Data` or JSON object. One of them should return `nil` to give access to other initializer. 
+
+In below, Response object will be created from the JSON response:
+
+```swift
+/// Initializes object from JSON response.
+class ExampleResponseObject: ResponseBodyParsable {
+    
+    var userId: Int
+    var id: Int
+    var title: String
+    var completed: Bool
+    
+    required init?(_ data: Data) {
+        return nil
+    }
+    
+    required init?(_ response: Any?) {
+        guard let dict = response as? [String:Any] else { return nil }
+        guard let userId = dict["userId"] as? Int,
+            let id = dict["id"] as? Int,
+            let title = dict["title"] as? String,
+            let completed = dict["completed"] as? Bool else { return nil }
+        
+        self.userId = userId
+        self.id = id
+        self.title = title
+        self.completed = completed
+        super.init(response)
+    }
+}
+```
+
+
+Or using data, for instance image, can be created by the data response:
+
+```swift
+/// Initializes object from Data.
+class ExampleImageObject: ResponseBodyParsable {
+    
+    var image: UIImage
+    
+    required init?(_ data: Data) {
+        guard let image = UIImage(data: data) else {
+            return nil
+        }
+        
+        self.image = image
+        super.init(data)
+    }
+    
+    required init?(_ response: Any?) {
+        return nil
+    }
+}
+```
+
+### Creating an API configuration
+
+Using highly customizable `APIConfiguration` object, API requests can be defined easily and requests from Network Layer.
+
+In below example, uses `ExampleResponseObject` as a response model to create API configuration with basic parameters. 
+
+```swift
+let api = APIConfiguration(hostURL: "https://jsonplaceholder.typicode.com",
+                           endPoint: "todos/1",
+                           responseBodyObject: ExampleResponseObject.self)
+
+```
+
+Or, advanced parameters can be applied.
+
+```swift
+let api = APIConfiguration(hostURL: "https://jsonplaceholder.typicode.com",
+                           endPoint: "todos/1",
+                           requestType: .get,
+                           headers: nil, body: nil,
+                           responseBodyObject: ExampleResponseObject.self,
+                           priority: .low,
+                           cachingTime: .init(seconds: 60),
+                           isMainOperation: false, autoCache: false)
+
+```
+
+### Requesting API from Network Layer
+
+When operation is completed, completion block will return with two cases, whether error or successful response.
+
+```swift
+guard let apiReq = api else {
+    print("Something wrong with the configuration")
+    return
+}
+
+apiReq.request { (result) in
+    switch result {
+    case .error(let errResponse):
+        print("Error: \(errResponse.error.localizedDescription)")
+    case .success(let successfulResponse):
+        print("Response Body: \(successfulResponse.responseBody)")
+    }
+}
+```
+
+## Advanced Usage
+
+### Defining AutoCache
+In default, responses will be cached by the given `cachingTime` property. However, `ResponseBodyParsable` gives flexibility to define time value dynamically from the object itself. By overriding `cachingEndsAt:` method from the object, new time value for cache expiry can be defined.
+
+In below, same example object overrides the method and uses, for instance one of the variables in the response to define caching expiry. 
+
+```swift
+/// Initializes object from JSON response.
+class ExampleResponseObject: ResponseBodyParsable {
+    
+    var userId: Int
+    var id: Int
+    var title: String
+    var completed: Bool
+    var expiry: Date?
+    
+    required init?(_ data: Data) {
+        return nil
+    }
+    
+    required init?(_ response: Any?) {
+        guard let dict = response as? [String:Any] else { return nil }
+        guard let userId = dict["userId"] as? Int,
+            let id = dict["id"] as? Int,
+            let title = dict["title"] as? String,
+            let completed = dict["completed"] as? Bool else { return nil }
+        
+        self.userId = userId
+        self.id = id
+        self.title = title
+        self.completed = completed
+        
+        // gets expiry value from the response
+        self.expiry = dict["expiry"] as? Date
+        
+        super.init(response)
+    }
+    
+    override func cachingEndsAt() -> Date? {
+        return self.expiry
+    }
+}
+```
+Then, in the API configuration, `autoCache` parameter should be set to `true`.
+ 
+### Operation Queues and priority of the requests
+`iOSUsefulNetworkLayer` holds two queues, one is called as `main` and the other one as `background`. In default, all request operations will be handled in the `background` queue unless `isMainOperation` property is set to `true`. It effects resource levels in the system level to use more resources, so requests which should needs to get answered and completed as soon as possible can moved into the `main` queue to use more resources from the system. 
+
+In addition, for the each request operation in the same queue will be handled by looking their `priority` specification. In default, all requests are marked as `normal` level, but by using that property more important requests can be moved into top by giving higher priority. 

Sources/iOSUsefulNetworkLayer/NetworkLayer/APIConfiguration.swift

@@ -58,7 +58,16 @@ public struct APIConfiguration<T> where T: ResponseBodyParsable {
     /**
      Initializes Configuration with the host URL and endpoint separately.
      Returns nil if request URL cannot be created successfuly.
+     - parameter hostURL: Base URL for the request. (e.g. "https://example.com")
+     - parameter endPoint: Endpoint for the API request. (e.g. "v1/api/test")
+     - parameter priority: Defines the priority of the operation in its queue.
+     - parameter timeOut: Timeout value for the request to fail if it cannot get answer from network in seconds. In default, it's 30 seconds.
+     - parameter cachingTime: Default caching time for the response, in default it's 1 hour.
+     - parameter requestType: Type of the request. In default it's `get`.
      - parameter isMainOperation: If `true`, operation will be performed in special queue and return to main queue.
+     - parameter headers: Headers for the API request. Don't need to add `content-Type` for JSON request bodies, which will be automatically added.
+     - parameter body: Request body for the API request.
+     - parameter responseBodyObject: Type of the Response Object to create.
      - parameter autoCache: To use that, override `cachingEndsAt:` method of Response Body Object.
      Then specified custom caching will be applied for that request.
      */
@@ -91,7 +100,15 @@ public struct APIConfiguration<T> where T: ResponseBodyParsable {
 
     /**
      Initializes Configuration with the URL
+     - parameter url: Request URL.
+     - parameter priority: Defines the priority of the operation in its queue.
+     - parameter timeOut: Timeout value for the request to fail if it cannot get answer from network in seconds. In default, it's 30 seconds.
+     - parameter cachingTime: Default caching time for the response, in default it's 1 hour.
+     - parameter requestType: Type of the request. In default it's `get`.
      - parameter isMainOperation: If `true`, operation will be performed in special queue and return to main queue.
+     - parameter headers: Headers for the API request. Don't need to add `content-Type` for JSON request bodies, which will be automatically added.
+     - parameter body: Request body for the API request.
+     - parameter responseBodyObject: Type of the Response Object to create.
      - parameter autoCache: To use that, override `cachingEndsAt:` method of Response Body Object.
      Then specified custom caching will be applied for that request.
      */