Basic Data

String

• ****String和NSString的差異：
  • String是值類型，NSString是參考類型
  • String可直接用 + 來串接字串， NSString要用append()
  • String支援for...in瀏覽方法（String.characters），NSString不支援
  • String計算字串長度用String.characters.count或String.lengthOfBytes(using: .utf8)；NSString用NSString.length
  • String用 == 比較兩字串是否相等，NSString用 NSString.isEqual(to: String)來比較字串，但是參數的字串要是String格式，也可以用NSString.isEqual(object: Any?)來比較兩物件是否相等
  • String轉數字用Int(String)，NSString用NSString.intValue
  • String判斷是否為空用String.isEmpty，NSString用NSString.length == 0
  • String可以用String.insert(newElement: Character, at: String.Index)來在特定字元前插入字元（不行插入字串）
• ****將NSData轉成String****
  • 方法 var string : String = NSString(data: data, encoding: NSUTF8StringEncoding)
  • 實例 var responseString = NSString(data: data!, encoding: String.Encoding.utf8.rawValue)
• 將Double轉成String的方式
  • let newStr = String(someDouble)

• 計算Image的size

  var image = info[UIImagePickerControllerOriginalImage] as! UIImage
  var imgData: NSData = NSData(data: UIImageJPEGRepresentation((image), 1)) 
  var imageSize: Int = imgData.length
  

• 抓取url的路徑

  if let path = urls?[indexPath.row] {
    cell.textLabel?.text = path.path
  }
  

• 找尋字串在另一個字串內的位置

  // 先找出要搜尋的字串在被搜尋字串內的Range
  let index = directory.absoluteString.range(of: documentURL.path, options: .backwards, range: directory.absoluteString.startIndex..<directory.absoluteString.endIndex, locale: nil)
  // 再用substring從某個index開始往後取剩下的字串
  let subDirectoryName = directory.absoluteString.substring(from: (index?.upperBound)!)
  

• 把字串內的空白字元移除掉

  let str = " Swift 3.0 "
  let trimmed = str.trimmingCharacters(in: .whitespacesAndNewlines)
  

• 檢查email格式

func isValidEmail(with email:String) -> Bool {

   print("validate emilId: \(email)")
   let emailRegEx = "[A-Z0-9a-z._%+-]+@[A-Za-z0-9.-]+\\.[A-Za-z]{2,4}"
   let emailTest = NSPredicate(format:"SELF MATCHES %@", emailRegEx)
   let result = emailTest.evaluate(with: email)
   return result
}

• Decode url格式的字串

let title = obj["title"].stringValue.removingPercentEncoding

• 計算字串長度

string1.characters.count

• 計算字串在Label內所需的高度

// extension String
func height(withConstrainedWidth width: CGFloat, font: UIFont) -> CGFloat {
    let constraintRect = CGSize(width: width, height: .greatestFiniteMagnitude)
    let boundingBox = self.boundingRect(with: constraintRect, options: .usesLineFragmentOrigin, attributes: [NSFontAttributeName: font], context: nil)

    return boundingBox.height
}
// 使用方式
let height =store.storeObj.about!.height(withConstrainedWidth: descriptionCell.contentLabel.frame.width, font: descriptionCell.contentLabel.font)

• 字串切割

let line = "apple,peach,kiwi"
// 將字串切割並塞入陣列
let parts = line.components(separatedBy: ",")
for part in parts {
    print(part)
}

Array

• Sort by date

let sortedArray = HistoryArray.sort({ $0.date.compare($1.date) == NSComparisonResult.OrderedDescending})

• forEach的用法

imageViews.forEach { $0?.isHidden = true }

• contain的用法

attendees.contains(where: { ($0 as AnyObject).sid == User.shared.sid })

• 陣列使用append()

  假設宣告一陣列 var directoryList:[URL]! 直接使用append()新增元素會遇到unwrapped error，原因是這時候的陣列還是nil狀態，所以要先給陣列值，像是 directoryList = getList() 或是宣告的時候就指定到空陣列 var directoryList:[URL]! = []

NSURL

• 獲取url最後的component

  let fileName = fileURL.lastPathComponent

Dictionary

• 宣告
  • var dic:<String, String> = Dictionary()
  • var dic = [String, String]()
  • var dic:[String, String] = [:]
  • var dic:[String, String] = Dictionary()
• 印在Console上
  • dump(dictionary)