MySubject

MySubject.swift

//
//  MySubject.swift
//  RxSwiftSample
//
//  Created by Yusuke on 4/10/16.
//  Copyright © 2016 Yusuke. All rights reserved.
//

import Foundation

class MySubject<T> {
    
    var value: T {
        didSet {
            observers.forEach{ $0(value) }
        }
    }
    
    private var observers: [T -> ()] = []
    
    init(value: T) {
        self.value = value
    }
    
    func describe(observer: T -> ()) {
        observers.append(observer)
    }
}

MySubjectTests.swift

//
//  MySubjectTests.swift
//  RxSwiftSample
//
//  Created by Yusuke on 4/10/16.
//  Copyright © 2016 Yusuke. All rights reserved.
//

import XCTest
@testable import RxSwiftSample

class MySubjectTests: XCTestCase {
    
    override func setUp() {
        super.setUp()
    }
    
    override func tearDown() {
        super.tearDown()
    }
    
    func testExample() {
        
        let expectation1 = self.expectationWithDescription("callback 1")
        let expectation2 = self.expectationWithDescription("callback 2")
        
        let subject: MySubject<Int> = MySubject(value: 1)
        
        // observer 1
        subject.describe {
            XCTAssertEqual($0, 2)
            expectation1.fulfill()
        }
        
        // observer 2
        subject.describe {
            XCTAssertEqual($0, 2)
            expectation2.fulfill()
        }
        
        // change observable
        subject.value = 2
        
        waitForExpectationsWithTimeout(0.3, handler: nil)
    }
}