added JSONSchemaValidatorHelper example and included in readme

Examples/JSONSchemaValidatorHelper.swift

@@ -0,0 +1,50 @@
+//
+//  JSONSchemaValidatorHelper.swift
+//
+//  Created by Geert Michiels on 24/01/2021.
+//
+
+import Foundation
+import JSONSchema
+import Combine
+
+struct JSONSchemaValidatorHelper {
+
+    private var fetchSchemaCancellable : AnyCancellable?
+
+    ///loads the json schema from the specified url (using combine framework aka publishers)
+    mutating func loadJsonSchema(url: URL, completion: @escaping ([String: Any]?) -> Void) {
+        fetchSchemaCancellable = URLSession.shared.dataTaskPublisher(for: url)
+            //after receiving the data from the load, convert it to jsonObject that is representing our schema
+            .map { data, urlResponse in
+                try? JSONSerialization.jsonObject(with: data, options: [])
+            }
+            //don't care about the url loading errors, just return nil schema if this happens
+            .replaceError(with: nil)
+            //go and call ourpassed in completion handler when finished
+            .sink { value in
+                completion(value as? [String:Any])
+            }
+    }
+
+    ///converts the specified encodable object to json and validates it agains the specified schema url
+    mutating func validate<Object>(encodableObject: Object, againstSchemaUrl schemaUrl: URL, completion: @escaping (ValidationResult?) -> Void ) where  Object: Encodable {
+        //first load our schema
+        loadJsonSchema(url: schemaUrl) { schema in
+            //check schema loaded successfully
+            guard let schema = schema else {
+                completion(ValidationResult.invalid(["Could not schema"]))
+                return
+            }
+            //convert our object to json
+            guard let jsonData   = (try? JSONEncoder().encode(encodableObject)),
+                  let jsonEquivalentFoundationObjects = (try? JSONSerialization.jsonObject(with: jsonData, options: [])) else {
+                completion(ValidationResult.invalid(["Could not convert 'encodableObject' to json equivalent foundation objects"]))
+                return
+            }
+            //perform validation and let our completion handler know the result
+            completion(JSONSchema.validate(jsonEquivalentFoundationObjects, schema: schema))
+        }
+    }
+
+}

README.md

@@ -14,6 +14,7 @@ pod 'JSONSchema'
 ```
 
 ## Usage
+### Basic
 
 ```swift
 import JSONSchema
@@ -27,8 +28,63 @@ JSONSchema.validate(["name": "Eggs", "price": 34.99], schema: [
   "required": ["name"],
 ])
 ```
+### JSONSchemaValidatorHelper.swift example
+Inside the `Example` folder you can find `JSONSchemaValidatorHelper.swift`.
+It shows how to load a json schema from a url and then validate it agains an object that confirms to the [Codable](https://developer.apple.com/documentation/swift/codable) protocol.
 
-### Error handling
+```swift
+struct JSONSchemaValidatorHelper {
+
+    private var fetchSchemaCancellable : AnyCancellable?
+
+    ///loads the json schema from the specified url (using combine framework aka publishers)
+    mutating func loadJsonSchema(url: URL, completion: @escaping ([String: Any]?) -> Void) {
+        fetchSchemaCancellable = URLSession.shared.dataTaskPublisher(for: url)
+            //after receiving the data from the load, convert it to jsonObject that is representing our schema
+            .map { data, urlResponse in
+                try? JSONSerialization.jsonObject(with: data, options: [])
+            }
+            //don't care about the url loading errors, just return nil schema if this happens
+            .replaceError(with: nil)
+            //go and call ourpassed in completion handler when finished
+            .sink { value in
+                completion(value as? [String:Any])
+            }
+    }
+
+    ///converts the specified encodable object to json and validates it agains the specified schema url
+    mutating func validate<Object>(encodableObject: Object, againstSchemaUrl schemaUrl: URL, completion: @escaping (ValidationResult?) -> Void ) where  Object: Encodable {
+        //first load our schema
+        loadJsonSchema(url: schemaUrl) { schema in
+            //check schema loaded successfully
+            guard let schema = schema else {
+                completion(ValidationResult.invalid(["Could not schema"]))
+                return
+            }
+            //convert our object to json
+            guard let jsonData   = (try? JSONEncoder().encode(encodableObject)),
+                  let jsonEquivalentFoundationObjects = (try? JSONSerialization.jsonObject(with: jsonData, options: [])) else {
+                completion(ValidationResult.invalid(["Could not convert 'encodableObject' to json equivalent foundation objects"]))
+                return
+            }
+            //perform validation and let our completion handler know the result
+            completion(JSONSchema.validate(jsonEquivalentFoundationObjects, schema: schema))
+        }
+    }
+
+}
+```
+
+This is how to use it:
+
+```swift
+        let schemaUrl = URL(string: "https://path.to.your.schema.json")!
+        jsonSchema.validate(encodableObject: snookerTable, againstSchemaUrl: schemaUrl) { result in
+            print(result)
+        }
+```
+
+## Error handling
 
 Validate returns an enumeration `ValidationResult` which contains all
 validation errors.