ios - 如何修复错误 : Binary operator '==' cannot be applied to operands of type 'NSExpression.ExpressionType' and '_'

Question

我正在查看来自 HomeKit Catalog: Creating Homes, Pairing and Controlling Accessories, and Setting Up Triggers 的旧代码当我遇到一个表示

的表达式时

.KeyPathExpressionType

我说不出来

.

在

.KeyPathExpressionType

是指左边的

.

当我在 Google 和堆栈溢出中搜索“KeyPathExpressionType”时，我什么也没找到。和

一样

.ConstantValueExpressionType

我什么也没找到。

每一个相等比较

comparison.leftExpression.expressionType == .KeyPathExpressionType

和

comparison.rightExpression.expressionType == .ConstantValueExpressionType

在下面的代码中，生成一条错误消息:

Binary operator '==' cannot be applied to operands of type 'NSExpression.ExpressionType' and '_'

extension NSPredicate {

    /**
        Parses the predicate and attempts to generate a characteristic-value `HomeKitConditionType`.

        - returns:  An optional characteristic-value tuple.
    */
    private func characteristic() -> HomeKitConditionType? {
        guard let predicate = self as? NSCompoundPredicate else { return nil }
        guard let subpredicates = predicate.subpredicates as? [NSPredicate] else { return nil }
        guard subpredicates.count == 2 else { return nil }

        var characteristicPredicate: NSComparisonPredicate? = nil
        var valuePredicate: NSComparisonPredicate? = nil

        for subpredicate in subpredicates {
            if let comparison = subpredicate as? NSComparisonPredicate, comparison.leftExpression.expressionType == .KeyPathExpressionType && comparison.rightExpression.expressionType == .ConstantValueExpressionType {
                switch comparison.leftExpression.keyPath {
                    case HMCharacteristicKeyPath:
                        characteristicPredicate = comparison

                    case HMCharacteristicValueKeyPath:
                        valuePredicate = comparison

                    default:
                        break
                }
            }
        }

        if let characteristic = characteristicPredicate?.rightExpression.constantValue as? HMCharacteristic,
            characteristicValue = valuePredicate?.rightExpression.constantValue as? NSCopying {
                return .Characteristic(characteristic, characteristicValue)
        }
        return nil
    }

当我替换时，错误消失了

comparison.leftExpression.expressionType == .KeyPathExpressionType

与

comparison.leftExpression.expressionType.rawValue == NSExpression.ExpressionType.keyPath.rawValue

和

comparison.rightExpression.expressionType == .ConstantValueExpressionType

与

comparison.rightExpression.expressionType.rawValue == NSExpression.ExpressionType.constantValue.rawValue

这是正确的吗？谁能告诉我这个问题的启发？

Answer 1

代码是过时的 Swift 2 代码。

将 .KeyPathExpressionType 替换为 .keyPath 并将 .ConstantValueExpressionType 替换为 .constantValue

类型是NSExpression.ExpressionType，请阅读documentation