如何比较可选字典？斯威夫特 3

Question

在 Swift 中我们可以比较 optionals，我们也可以比较字典，但是如何比较 optional Dictionaries？

var dict: [String: String]? = [
    "name" : "A name",
    "email" : "an@email.com"
]
var dict2 = [
    "name" : "A name",
    "email" : "an@email.com"
]


if dict2 == dict {   // Error line: Value of optional type '[String : String]?' not unwrapped; did you mean to use '!' or '?'?

}

这不会编译并迫使我们打开字典。有什么干净的解决方案吗？

Answer 1

解开您的字典实例，然后尝试比较它。

使用if-let 块

let dict: [String: String]? = [
   "name" : "A name",
   "email" : "an@email.com"
]

let dict2 = [
   "name" : "A name",
   "email" : "an@email.com"
]

// use if-let 
if let dict1 = dict, dict2 == dict1 {
   print("true")    // result is "true"
} else {
   print("false")
}

字典“名称”的更新值

let dict3 = [
   "name" : "B name",
   "email" : "an@email.com"
]

// use if-let 
if let dict1 = dict, dict3 == dict1 {
   print("true")  
} else {
   print("false")  // result is "false"
}