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如何运行一系列函数,如果其中一个函数执行,则返回

swift ios

Tometoyou · 技术社区 · 6 年前

我在PrepareForSegue函数中初始化容器视图控制器,如下所示:

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    initialiseTopViewController(for: segue)
    initialiseMessagesViewController(for: segue)
    initialiseToolbarViewController(for: segue)
    initialiseTicketViewController(for: segue)
}

由于 guard SEgue标识符上的条件。我如何才能使它这样做:如果其中一个函数执行,它就不会继续尝试执行其他函数?有比单纯使用更好的方法吗 if...else if 阻碍

4 回复 | 直到 6 年前

Gereon 6 年前

类似于@rob mayoff的建议,让每个函数返回 Bool 循环通过一个包含所有这些元素的数组,使其完全由数据驱动。

func prepare(for segue: UIStoryboardSegue, sender: Any?) {
   let funs = [ initialiseTopViewController(for:), 
                initialiseMessagesViewController(for:), 
                initialiseToolbarViewController(for:), 
                initialiseTicketViewController(for:) ]

   for fun in funs {
       if fun(segue) {
           break
       }
   }
}

rob mayoff 6 年前

一个解决方案是 initialise 函数返回 true 如果它处理信号,否则 false . 然后:

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    _ = (false
        || initialiseTopViewController(for: segue)
        || initialiseMessagesViewController(for: segue)
        || initialiseToolbarViewController(for: segue)
        || initialiseTicketViewController(for: segue)
    )
}

private func initialiseTopViewController(for segue: UIStoryboardSegue) -> Bool { ... }
private func initialiseMessagesViewController(for segue: UIStoryboardSegue) -> Bool { ... }
private func initialiseToolbarViewController(for segue: UIStoryboardSegue) -> Bool { ... }
private func initialiseTicketViewController(for segue: UIStoryboardSegue) -> Bool { ... }

另一种解决方案是将适当的测试提升到 prepare(for:sender:) ,例如使用 switch :

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    switch (segue.identifier ?? "", segue.destination) {
        case (_, let dest as TopViewController): initialiseTopViewController(dest)
        case (_, let dest as MessagesViewController): initialiseMessagesViewController(dest)
        case ("toolbar", let dest as MultipurposeViewController): initialiseToolbarViewController(dest)
        case ("ticket", let dest as MultipurposeViewController): initialiseTicketViewController(dest)
        default: super.prepare(for: segue, sender: sender)
    }
}

private func initialiseTopViewController(_ controller: TopViewController) { ... }
private func initialiseMessagesViewController(_ controller: MessagesViewController) { ... }
private func initialiseToolbarViewController(_ controller: MultipurposeViewController) { ... }
private func initialiseTicketViewController(_ controller: MultipurposeViewController) { ... }

Rob Md Fahim Faez Abir 6 年前

我建议一个 switch 检查/强制转换的语句 destination 对于各种类型,并将该类型值传递给适当的方法:

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    switch segue.destination {
    case let destination as FooViewController: prepare(destination)
    case let destination as BarViewController: prepare(destination)
    case let destination as BazViewController: prepare(destination)
    default: super.prepare(for: segue, sender: sender)
    }
}

func prepare(_ destination: FooViewController) {
    destination.foo = foo
}

func prepare(_ destination: BarViewController) {
    destination.bar = bar
}

func prepare(_ destination: BazViewController) {
    destination.baz = baz
}

这个 转换 只调用适当的方法并保存这些独立的方法,而不需要执行任何 guard 声明。

hackerman58888 6 年前

我想添加到@rob mayoff的解决方案中,使函数返回 bool

// make each function return boolean values so you know if it executed properly or not based on the return value
func initialiseTopViewController(for segue: UIStoryboardSegue) -> Bool { ... }
func initialiseMessagesViewController(for segue: UIStoryboardSegue) -> Bool { ... }
func initialiseToolbarViewController(for segue: UIStoryboardSegue) -> Bool { ... }
func initialiseTicketViewController(for segue: UIStoryboardSegue) -> Bool { ... }

override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
    // if any function returns true, then return and don't run the remaining functions
    if initialiseTopViewController(for: segue) { return }
    if initialiseMessagesViewController(for: segue) { return }
    if initialiseToolbarViewController(for: segue) {return }
    if initialiseTicketViewController(for: segue) { return }
}

如果这和其他建议类似,我很抱歉。我只是想向您展示如何使用内联if语句轻松实现。