Swift：從字符串中提取子字符串

Question

我有一個可以是以下任一類型的字符串：

tempString = "What? The ID: 54673 Over there"
tempString = "Jump... ID: 4561E how high"

基本上，我想從字符串中檢索五個字符的 ID：。 對於大多數語言，我可以通過查找 ID: 來實現這一點，向其添加 4 以到達 ID: 的開頭，然后獲取接下來的五個字符。

例如，在 Excel 中：

=MID("Jump... ID: 4561E how high",FIND("ID:","Jump... ID: 4561E how high")+4, 5)

將 = 4561E。

我們如何用 Swift 做到這一點？

Answer 1

您可以在字符串上使用range(of:)來查找子字符串的range ，然后使用該range的upperBound索引原始字符串以獲取從該點開始的子字符串。 最后， prefix(5)允許您獲取該子字符串的前 5 個字符， String()將Substring.Subsequence回正常的String ：

if let range = tempString.range(of: "ID: ") {
    let ident = String(tempString[range.upperBound...].prefix(5))
    print(ident)
}

注意： range(of:)來自Foundation框架，因此需要import Foundation或import其他使用Foundation框架，例如UIKit或Cocoa 。

Answer 2

在“ID:”之后從 [0-9] 或 [AF] 中查找前 5 個字符的正則表達式方法（僅在不能使用 AZ 的情況下才使用十六進制字母）。

if let range = string.range(of: "(?<=ID: )[0-9A-F]{5}", options: .regularExpression) {
    let id = string[range]  // 
    // if you need a String instead of a substring
    let stringID = String(string[range])
}

---

編輯/更新：

查看您的答案，看起來要求與您的原始帖子完全不同，無論如何要找到 8 個十六進制字符后跟連字符的 IF 復合，然后是 4 個六進制字符后跟連字符（3 次）而不是 12 個十六進制字符，您可以使用以下正則表達式"([0-9a-f]{8}-)([0-9a-f]{4}-){3}([0-9a-f]{12})" ：

---

let dataString = """
{
  "@odata.context": "$metadata#GeoFences(Points())/$entity",
  "ID": "2b2a2abc-5962-4290-92b4-773025ffd50b",
  "Points": {
    "POINT_TYPE": "F",
    "POINT_NUM": 0,
    "LATITUDE": 32.92197686725423,
    "LONGITUDE": -117.04306932263532,
    "parent_ID": "2b2a2abc-5962-4290-92b4-773025ffd50b"
  },
  "GEOFENCE_NAME": "New Fence",
  "GEOFENCE_TYPE": "O",
  "PRIVACY": "X",
  "CENTER_LAT": 32.92043316309709,
  "CENTER_LONG": -117.04286922250975,
  "ZOOM_LAT": 0.006238797350533787,
  "ZOOM_LONG": 0.005345531926053582,
  "PATH_TOLERANCE": 5,
  "ENTRANCE_TOLERANCE": 5
}
"""

---

if let range = dataString.range(of: "([0-9a-f]{8}-)([0-9a-f]{4}-){3}([0-9a-f]{12})", options: .regularExpression) {
    let id = dataString[range]  // 4561E
    print("ID:", id)
    // if you need a String instead of a substring
    let stringID = String(dataString[range])
    print("stringID:", stringID)
}

---

這將打印

編號：2b2a2abc-5962-4290-92b4-773025ffd50b

字符串 ID：2b2a2abc-5962-4290-92b4-773025ffd50b

---

請注意，您的代碼將導致"2b2a2abc-5962-4290-92b4-773025ffd50

---

編輯/更新2：

考慮到您的字符串是 JSON，您可以簡單地解碼您的字符串 id：

struct Root: Codable {
    let id: String
    enum CodingKeys: String, CodingKey {
        case id = "ID"
    }
}
do {
    let id = try JSONDecoder().decode(Root.self, from: Data(dataString.utf8)).id
    print(id)  // "2b2a2abc-5962-4290-92b4-773025ffd50b"
} catch {
    print(error)
}

---

如果您需要解碼所有數據：

struct Root: Codable {
    let odataContext, id: String
    let points: Points
    let geofenceName, geofenceType, privacy: String
    let centerLat, centerLong, zoomLat, zoomLong: Double
    let pathTolerance, entranceTolerance: Int

    enum CodingKeys: String, CodingKey {
        case odataContext = "@odata.context", id = "ID", points = "Points", geofenceName = "GEOFENCE_NAME", geofenceType = "GEOFENCE_TYPE", privacy = "PRIVACY", centerLat = "CENTER_LAT", centerLong = "CENTER_LONG", zoomLat = "ZOOM_LAT", zoomLong = "ZOOM_LONG", pathTolerance = "PATH_TOLERANCE", entranceTolerance = "ENTRANCE_TOLERANCE"
    }
}

---

struct Points: Codable {
    let pointType: String
    let pointNum: Int
    let latitude, longitude: Double
    let parentID: String

    enum CodingKeys: String, CodingKey {
        case pointType = "POINT_TYPE", pointNum = "POINT_NUM", latitude = "LATITUDE", longitude = "LONGITUDE", parentID = "parent_ID"
    }
}

---

do {
    let root = try JSONDecoder().decode(Root.self, from: Data(dataString.utf8))
    print("ID:", root.id)  // ID: 2b2a2abc-5962-4290-92b4-773025ffd50b
    print("Root:", root)   // Root: Root(odataContext: "$metadata#GeoFences(Points())/$entity", id: "2b2a2abc-5962-4290-92b4-773025ffd50b", points: __lldb_expr_111.Points(pointType: "F", pointNum: 0, latitude: 32.92197686725423, longitude: -117.04306932263532, parentID: "2b2a2abc-5962-4290-92b4-773025ffd50b"), geofenceName: "New Fence", geofenceType: "O", privacy: "X", centerLat: 32.92043316309709, centerLong: -117.04286922250975, zoomLat: 0.0062387973505337885, zoomLong: 0.005345531926053582, pathTolerance: 5, entranceTolerance: 5)
} catch {
    print(error)
}

Answer 3

對於您的情況，可以使用 NSRegularExpression：

let tempString1 = "What? The ID: 54673 Over there"
let tempString2 = "Jump... ID: 4561E how high"

func matches(for regex: String, in text: String) -> [String] {
    do {
        let regex = try NSRegularExpression(pattern: regex)
        let results = regex.matches(in: text,
                                    range: NSRange(text.startIndex..., in: text))
        return results.map {
            String(text[Range($0.range, in: text)!])
        }
    } catch let error {
        print("invalid regex: \(error.localizedDescription)")
        return []
    }
}

var res1 = matches(for: "[0-9]+[A-Z]*", in: tempString1) // 54673
var res2 = matches(for: "[0-9]+[A-Z]*", in: tempString2) // 4561E

Answer 4

好的，我開始這個練習是因為我懶得解碼 JSON，因為我必須構建結構並使它們正確。 所以，我想我會很快做一個子串。 好吧，解碼會更好、更快、更准確，但我將在下面展示我的代碼。 基本上，我想從 JSON 字符串中獲取 ID：

{
  "@odata.context": "$metadata#GeoFences(Points())/$entity",
  "ID": "2b2a2abc-5962-4290-92b4-773025ffd50b",
  "Points": {
    "POINT_TYPE": "F",
    "POINT_NUM": 0,
    "LATITUDE": 32.92197686725423,
    "LONGITUDE": -117.04306932263532,
    "parent_ID": "2b2a2abc-5962-4290-92b4-773025ffd50b"
  },
  "GEOFENCE_NAME": "New Fence",
  "GEOFENCE_TYPE": "O",
  "PRIVACY": "X",
  "CENTER_LAT": 32.92043316309709,
  "CENTER_LONG": -117.04286922250975,
  "ZOOM_LAT": 0.006238797350533787,
  "ZOOM_LONG": 0.005345531926053582,
  "PATH_TOLERANCE": 5,
  "ENTRANCE_TOLERANCE": 5
}

我的代碼如下。 我很快就會用解碼替換它。 變量 id 確實包含 id。

var foundI :Bool = false
var iIndex = 0
for (index, char) in dataString.enumerated() {
    if char == "I" {
        foundI = true
        iIndex = index
    } else if char == "D" {
        if foundI == true && index == iIndex+1 {
           var suffixStr =  String(dataString.dropFirst(iIndex+5))
           var id = String(suffixStr.prefix(36))
        
            print("New String \(id)")
        }
    }
}