swift - 如何正确处理多个 if else 条件？

Question

我有三个条件:

1. data.weight 和myoutput 都是nil
2. myoutput 没有值

3. data.weight 和 myoutput 都有值

   override func viewWillAppear(_ animated: Bool) {
       super .viewWillAppear(animated)
       self.navigationItem.hidesBackButton = true
   
       let myOutput = UserDefaults.standard.string(forKey: "height")
       let dateFormator = DateFormatter()
       dateFormator.dateFormat = "dd.MM.yyyy"
       let data = WeightTracker.mr_findFirst(with: NSPredicate(format: "date == %@", dateFormator.string(from: Date()))) as? WeightTracker
   
       if myOutput == nil && data?.weight == nil {
           bmiLabel.text = "--"
       } else if myOutput == nil && data?.weight != nil {
           bmiLabel.text = "--"
       } else {
           let dateFormator = DateFormatter()
           dateFormator.dateFormat = "dd.MM.yyyy"
           if let data = WeightTracker.mr_findFirst(with: NSPredicate(format: "date == %@", dateFormator.string(from: Date()))) as? WeightTracker {
               let myOutput: AnyObject? = UserDefaults.standard.object(forKey: "height") as AnyObject
               var sum = (myOutput as! NSString).doubleValue / 1000
               let total1 = sum * sum
               let total = Double(Int(data.weight!)!) / total1
               let dye = total/100.00
               bmiLabel.text = String(dye)
           }
       }
   }
   

只应为第三个条件计算总和。处理此问题的正确方法是什么？

Answer 1

if let myOutput = UserDefaults.standard.string(forKey: "height") as? NSString , let weight = data?.weight {
    let dateFormator = DateFormatter()
    dateFormator.dateFormat = "dd.MM.yyyy"
    if let data = WeightTracker.mr_findFirst(with: NSPredicate(format: "date == %@", dateFormator.string(from: Date()))) as? WeightTracker{
        var sum = myOutput.doubleValue   / 1000
        let total1 = sum * sum
        let total = Double(Int(weight)!) / total1
        let dye = total/100.00

        bmiLabel.text = String(dye)
    }
} else {
    bmiLabel.text = "--"
}