如何比較可選詞典？ 斯威夫特3

Question

在Swift中我們可以比較選項，我們也可以比較字典，但如何比較可選的字典？

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 '?'?

}

這不會編譯並強制我們解開字典。 有清潔的解決方案

Answer 1

解開您的字典實例，然后嘗試比較它。

使用if-let塊

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“名稱”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"
}