Yang "Ino" Popper | iOS Engineer

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the making of Bitcoin Ticker app

ino .

Click to download project open source on my Github repo :)

It’s simply a bitcoin currency exchange rate app, as a sister app of the weather app from the previous blog. So I will not repeat the in-depth code breakdown since it’s very similar and even simpler.

Here is a snippet of the project:

  • ViewController.swift

import UIKit

class ViewController: UIViewController {
    
    @IBOutlet weak var bitcoinLabel: UILabel!
    @IBOutlet weak var currencyLabel: UILabel!
    @IBOutlet weak var currencyPicker: UIPickerView!
    
    var coinManager = CoinManager()
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        coinManager.delegate = self
        currencyPicker.dataSource = self
        currencyPicker.delegate = self
    }
}

//MARK: - CoinManagerDelegate

extension ViewController: CoinManagerDelegate {
    
    func didUpdatePrice(price: String, currency:String) {
        
        DispatchQueue.main.async {
            self.bitcoinLabel.text = price
            self.currencyLabel.text = currency
        }
    }
    
    func didFailWithError(error: Error) {
        print(error)
    }
}

//MARK: - UIPickerView DataSource & Delegate

extension ViewController: UIPickerViewDataSource, UIPickerViewDelegate {
    
    func numberOfComponents(in pickerView: UIPickerView) -> Int {
        return 1
    }
    
    func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
        coinManager.currencyArray.count
    }
    
    func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {
        return coinManager.currencyArray[row]
    }
    
    func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {
        let selectedCurrency = coinManager.currencyArray[row]
        coinManager.getCoinPrice(for: selectedCurrency)
    }
}

  • CoinData.swift

import Foundation

struct CoinData: Codable {
    let rate: Double
}

  • CoinManager.swift

import Foundation

protocol CoinManagerDelegate {
    
    func didUpdatePrice(price: String, currency: String)
    func didFailWithError(error: Error)
}

struct CoinManager {
    
    var delegate: CoinManagerDelegate?
    
    let baseURL = "https://rest.coinapi.io/v1/exchangerate/BTC"
    let apiKey = "YOUR_API_KEY"
    
    let currencyArray = ["AUD", "BRL","CAD","CNY","EUR","GBP","HKD","IDR","ILS","INR","JPY","MXN","NOK","NZD","PLN","RON","RUB","SEK","SGD","USD","ZAR"]
    
    func getCoinPrice(for currency: String) {
        
        let urlString = "\(baseURL)/\(currency)?apikey=\(apiKey)"
        
        if let url = URL(string: urlString) {
            
            let session = URLSession(configuration: .default)
            let task = session.dataTask(with: url) { (data, response, error) in
                if error != nil {
                    self.delegate?.didFailWithError(error: error!)
                    return
                }
                
                if let safeDate = data {
                    
                    if let bitcoinPrice = self.parseJSON(safeDate) {
                        
                        let priceString = String(format: "%.2f", bitcoinPrice)
                        
                        self.delegate?.didUpdatePrice(price: priceString, currency: currency)
                    }
                }
            }
            task.resume()
        }
    }
    
    func parseJSON(_ data: Data) -> Double? {
            let decoder = JSONDecoder()
            do {
                let decodedData = try decoder.decode(CoinData.self, from: data)
                let lastPrice = decodedData.rate
                print(lastPrice)
                return lastPrice

            } catch {
                
                delegate?.didFailWithError(error: error)
                return nil
            }
        }
}