如何在代码中创建大小为 类 的 UITraitCollection？

Question

我有一个简单的扩展 UITraitCollection:

extension UITraitCollection {

    var isIpad: Bool {
        return horizontalSizeClass == .Regular && verticalSizeClass == .Regular
    }
}

之前，我需要为此编写测试（使用 TDD）：

let traitCollection = UITraitCollection(verticalSizeClass: .Regular) //the init is either for vertical or horizontal at time
traitCollection.horizontalSizeClass = .Regular //error

XCTAssertTrue(traitCollection.isIpad)

但错误是：

Cannot assign to property: horizontalSizeClass is a get only property.

那我该怎么办？

Answer 1

好的，我找到了解决方案：

let compactTraitCollection = UITraitCollection(traitsFromCollections: [UITraitCollection(verticalSizeClass: .Compact), UITraitCollection(horizontalSizeClass: .Compact)])
XCTAssertFalse(compactTraitCollection.isIpad)

let regularTraitCollection = UITraitCollection(traitsFromCollections: [UITraitCollection(verticalSizeClass: .Regular), UITraitCollection(horizontalSizeClass: .Regular)])
XCTAssertTrue(regularTraitCollection.isIpad)