Question

iOS手势识别器遍历不同的状态。在第一个开始状态下捕获参考状态是常见的（至少对我来说）。在ObjectiveC中，可能看起来像：

using System.Collections.Generic;
using System.Linq;
using NUnit.Framework;

[TestFixture]
public class SqlStringExtensionsTests
{
    [Test]
    public void ValidateSql_InvalidSql_ReturnsErrorMessages()
    {
        // this example doesn't contain "," between the field names
        string invalidSql = "SELECT /*comment*/ " +
            "CustomerID AS ID CustomerNumber FROM Customers";
        IEnumerable<string> results = invalidSql.ValidateSql();
        Assert.AreNotEqual(0, results.Count());
    }

    [Test]
    public void IsValidSql_ValidSql_ReturnsTrue()
    {
        string validSql = "SELECT /*comment*/ " +
            "CustomerID AS ID, CustomerNumber FROM Customers";
        bool result = validSql.IsValidSql();
        Assert.AreEqual(true, result);
    }

    [Test]
    public void IsValidSql_InvalidSql_ReturnsFalse()
    {
        // this example doesn't contain "," between the field names
        string invalidSql = "SELECT /*comment*/ "+
            " CustomerID AS ID CustomerNumber FROM Customers";
        bool result = invalidSql.IsValidSql();
        Assert.AreEqual(false, result);
    }
}

但是Swift没有静态函数变量来保存函数执行之间的值。我可以在类级别将这些变量转换为- (void)pan:(UIPanGestureRecognizer *)pan { static NSTimeInterval originalBegin; static NSTimeInterval originalEnd; static CGFloat originalYOffset; if (pan.state == UIGestureRecognizerStateBegan) { originalBegin = self.timeAxis.begin; originalEnd = self.timeAxis.end; originalYOffset = self.yOffset; } ... } s，但是它会污染对象的变量空间，仅适用于仅附加到特定识别器的变量。

是否有Swift习惯方式在本地捕获此模式？或者这是Swift与UIKit摩擦的领域之一。

Answer 1

在Swift中，您可以在函数中嵌套struct，class或enum定义，并在运行之间保持静态状态。例如：

func run() {
    enum State { static var counter = 0 }
    State.counter += 1
    print(State.counter)
}

run()
run()
run()

Swift惯用法捕获手势识别器开始状态

1 个答案: