swift - 无法过滤对象数组

Question

我试图通过对象数组的属性之一来过滤它。尝试了很多解决方案，但在我开始输入后抛出错误

//我的模型类

class Book{

var bookId:Int?

var bookName:String?

//omitted init function

}

// View Controller //这是我的文本字段委托(delegate)方法

let myArray:[Book] = [Book(bookId:23,bookName:"book1"),Book(bookId:53,bookName:"book2"),Book(bookId:43,bookName:"book3"),] 

func textField(_ textField: UITextField, shouldChangeCharactersIn 

range: NSRange, replacementString string: String) -> Bool 
{

       lastCharactar = string

        textFieldText = myTextField.text! + lastCharactar

        let predicate = NSPredicate(format: "ANY SELF.bookName BEGINSWITH %@", textFieldText)

        let arr = ( myArray as NSArray).filtered(using: predicate)

        return true
    }

I am getting the following error
"this class is not key value coding-compliant for the key bookName."

Answer 1

Swift Array 不需要谓词来过滤其内容。 Swift 数组有 filter 方法来过滤数组。例如:

struct Book{
    var bookId:Int?
    var bookName:String?
}

let myArray:[Book] = [Book(bookId:23,bookName:"book1"),Book(bookId:53,bookName:"book2"),Book(bookId:43,bookName:"book3"),]

func textField(_ textField: UITextField, shouldChangeCharactersIn 
range: NSRange, replacementString string: String) -> Bool 
{
    lastCharactar = string
    textFieldText = myTextField.text! + lastCharactar

    let arr = myArray.filter { (book) -> Bool in
      if let name = book.bookName, name.hasPrefix(textFieldText) {
        return true
      }
      return false
    }

   return true
 }

注意:结构是一种值类型，当将其分配给变量或常量或传递给函数时，其值会被复制，而类是引用类型，默认情况下不会复制其值。