如果弱则检查Swift协议属性

Question

如果类属性是弱的或者不是弱的，那么在XCTest中是否可以测试它。

class A {
  weak var p: String? = nil
}

结果:如果类的p属性是弱的，则断言为

Answer 1

您可以使用这样的方法：

class TestObject {}

protocol A {
    var a: TestObject? { get set }
}

class B: A {
    var a: TestObject?
}

class C: A {
    weak var a: TestObject?
}

func addVar(to: A) {
    var target = to
    target.a = TestObject()  // Once we leave the scope of this function, the TestObject instance created here will be released unless retained by target
}

let b = B()
let c = C()

addVar(to: b)
addVar(to: c)

print(b.a)  // prints Optional(TestObject) because class C uses a strong var for a
print(c.a)  // prints nil because class B uses a weak var for a

转换为测试用例时，它可能如下所示：

func testNotWeak() {

    func addVar(to: A) {
        var target = to
        target.a = TestObject()  // Once we leave the scope of this function, the TestObject instance created here will be released unless retained by target
    }

    let testClass = B()
    addVar(to: testClass)
    XCTAssertNotNil(testClass.a)
}