Swift：如何将数组中的值从字符串更改为浮点数

Question

我有一个函数可以进行 api 调用并创建一个数组。

功能：

func getData(_ completion: @escaping ([Any]) -> ()) {
  let urlPath = "https://gradual-deploy.vercel.app/students/currentclasses?username=john&password=doe"
            
    guard let url = URL(string: urlPath) else { return }
            
    let task = URLSession.shared.dataTask(with: url) { (data, response, error) in
      guard let data = data else { return }
        do {
          if let jsonResult = try JSONSerialization.jsonObject(with: data, options: JSONSerialization.ReadingOptions.mutableContainers) as? NSDictionary {
              let results = jsonResult["currentClasses"] as! [Any]
               completion(results)
              }
                } catch {
                    
          }
}
    task.resume()
}

json返回：

[{
  "currentClasses": [
    {
      "name": "CATE27600B - 3    Mobile App Programming S2@CTEC",
      "grade": "",
      "weight": "6",
      "credits": "1"
      "Last Updated": "",
      "assignments": []
    },

    {
      "name": "CATE36400B - 1    Prac News Prod 2 S2",
      "grade": "",
      "weight": "5",
      "credits": "1",
      "Last Updated": "1/6/2022",
      "assignments": [
        {
          "assignment": "PA Script #3",
          "category": "Minor Grades",
          "dateAssigned": "02/09/2022",
          "dateDue": "03/04/2022",
          "score": "",
          "totalPoints": "100.00"
        },
        {
          "assignment": "Social Media Posts",
          "category": "Minor Grades",
          "dateAssigned": "01/04/2022",
          "dateDue": "03/02/2022",
          "score": "",
          "totalPoints": "100.00"
        },
        {
          "assignment": "MP3 Package/Segment #2",
          "category": "Major Grades",
          "dateAssigned": "01/10/2022",
          "dateDue": "03/02/2022",
          "score": "",
          "totalPoints": "100.00"
        },
        {
          "assignment": "Event Coverage",
          "category": "Major Grades",
          "dateAssigned": "01/04/2022",
          "dateDue": "02/25/2022",
          "score": "",
          "totalPoints": "100.00"
        },
        {
          "assignment": "PA Script #2",
          "category": "Minor Grades",
          "dateAssigned": "01/24/2022",
          "dateDue": "02/08/2022",
          "score": "",
          "totalPoints": "100.00"
        },
        {
          "assignment": "MP3 Package/Segment #1",
          "category": "Major Grades",
          "dateAssigned": "01/11/2022",
          "dateDue": "02/04/2022",
          "score": "",
          "totalPoints": "100.00"
        },
        {
          "assignment": "PA Script #1",
          "category": "Minor Grades",
          "dateAssigned": "01/04/2022",
          "dateDue": "01/21/2022",
          "score": "97.00",
          "totalPoints": "100.00"
        },
        {
          "assignment": "MP3 Calendar Check",
          "category": "Non-graded",
          "dateAssigned": "01/04/2022",
          "dateDue": "01/06/2022",
          "score": "100.0",
          "totalPoints": "100.00"
        }
      ]
    },

    {
      "name": "ELA14300B - 4    AP English Literature S2",
      "grade": "85.00",
      "weight": "6",
      "credits": "1",
      "Last Updated": "1/13/2022",
      "assignments": [
        {
          "assignment": "Thesis Practice #1",
          "category": "Minor Grades",
          "dateAssigned": "",
          "dateDue": "01/13/2022",
          "score": "90.00",
          "totalPoints": "100.00"
        },
        {
          "assignment": "Christmas Carol Q3 Essay",
          "category": "Minor Grades",
          "dateAssigned": "",
          "dateDue": "01/05/2022",
          "score": "80.00",
          "totalPoints": "100.00"
        }
      ]
    },

    {
      "name": "MTH45300B - 1    AP Calculus AB S2",
      "grade": "80.80",
      "weight": "6",
      "credits": "1",
      "Last Updated": "1/10/2022",
      "assignments": [
        {
          "assignment": "Unit 6 Test (Integration)",
          "category": "Major Grades",
          "dateAssigned": "",
          "dateDue": "02/08/2022",
          "score": "",
          "totalPoints": "100.00"
        },
        {
          "assignment": "Delta Math Practice (Unit 6)",
          "category": "Minor Grades",
          "dateAssigned": "",
          "dateDue": "02/08/2022",
          "score": "",
          "totalPoints": "100.00"
        },
        {
          "assignment": "Quiz 4 (Antiderivatives and Rules of Integration)",
          "category": "Minor Grades",
          "dateAssigned": "",
          "dateDue": "01/31/2022",
          "score": "",
          "totalPoints": "100.00"
        },
        {
          "assignment": "Quiz 3 (FTC and Definite Integrals)",
          "category": "Minor Grades",
          "dateAssigned": "",
          "dateDue": "01/27/2022",
          "score": "",
          "totalPoints": "100.00"
        },
        {
          "assignment": "Quiz 2 (Properties of Def. Integrals)",
          "category": "Minor Grades",
          "dateAssigned": "",
          "dateDue": "01/25/2022",
          "score": "",
          "totalPoints": "100.00"
        },
        {
          "assignment": "Quiz 1 (Reimann Sums and Definite Integrals)",
          "category": "Minor Grades",
          "dateAssigned": "",
          "dateDue": "01/19/2022",
          "score": "",
          "totalPoints": "100.00"
        },
        {
          "assignment": "Unit 5 Test (Analytical Applications of Derivatives)",
          "category": "Major Grades",
          "dateAssigned": "",
          "dateDue": "01/10/2022",
          "score": "78.00",
          "totalPoints": "100.00"
        },
        {
          "assignment": "Delta Math Practice (Unit 5)",
          "category": "Minor Grades",
          "dateAssigned": "",
          "dateDue": "01/10/2022",
          "score": "85.00",
          "totalPoints": "100.00"
        }
      ]
    },

    {
      "name": "MTH45310B - 4    AP Statistics S2",
      "grade": "0.00",
      "weight": "6",
      "credits": "1",
      "Last Updated": "",
      "assignments": [
        {
          "assignment": "Test - 8 Confidence Intervals",
          "category": "Major Grades",
          "dateAssigned": "",
          "dateDue": "01/26/2022",
          "score": "",
          "totalPoints": "100.00"
        },
        {
          "assignment": "Skills Check - 8 Confidence Intervals",
          "category": "Minor Grades",
          "dateAssigned": "",
          "dateDue": "01/24/2022",
          "score": "",
          "totalPoints": "100.00"
        },
        {
          "assignment": "Practice - 8.3 (canvas)",
          "category": "Non-graded",
          "dateAssigned": "",
          "dateDue": "01/24/2022",
          "score": "",
          "totalPoints": "100.00"
        },
        {
          "assignment": "Practice - 8.2 (canvas)",
          "category": "Non-graded",
          "dateAssigned": "",
          "dateDue": "01/24/2022",
          "score": "",
          "totalPoints": "100.00"
        },
        {
          "assignment": "Practice - 8.1 (canvas)",
          "category": "Non-graded",
          "dateAssigned": "",
          "dateDue": "01/24/2022",
          "score": "",
          "totalPoints": "100.00"
        },
        {
          "assignment": "Group Skills Check - 7 Sampling Distributions",
          "category": "Minor Grades",
          "dateAssigned": "",
          "dateDue": "01/11/2022",
          "score": "",
          "totalPoints": "50.00"
        }
      ]
    },

    {
      "name": "SCI43300B - 1    AP Environmental Science S2",
      "grade": "",
      "weight": "6",
      "credits": "1",
      "Last Updated": "",
      "assignments": []
    },

    {
      "name": "SST34300 - 4    AP Government",
      "grade": "0.00",
      "weight": "6",
      "credits": "1",
      "Last Updated": "",
      "assignments": [
        {
          "assignment": "Midterm Exam (Units 1 & 2)",
          "category": "Major Grades",
          "dateAssigned": "",
          "dateDue": "02/23/2022",
          "score": "",
          "totalPoints": "100.00"
        },
        {
          "assignment": "Unit 2 Major Grade FRQ",
          "category": "Major Grades",
          "dateAssigned": "",
          "dateDue": "02/16/2022",
          "score": "",
          "totalPoints": "100.00"
        },
        {
          "assignment": "Unit 2 MC Quiz",
          "category": "Minor Grades",
          "dateAssigned": "",
          "dateDue": "02/14/2022",
          "score": "",
          "totalPoints": "100.00"
        },
        {
          "assignment": "Unit 2 Argument FRQ Practice",
          "category": "Minor Grades",
          "dateAssigned": "",
          "dateDue": "02/11/2022",
          "score": "",
          "totalPoints": "100.00"
        },
        {
          "assignment": "Unit 2 Congress FRQ Practice",
          "category": "Minor Grades",
          "dateAssigned": "",
          "dateDue": "02/04/2022",
          "score": "",
          "totalPoints": "100.00"
        },
        {
          "assignment": "Unit 1 Major Grade FRQ",
          "category": "Major Grades",
          "dateAssigned": "",
          "dateDue": "01/21/2022",
          "score": "",
          "totalPoints": "100.00"
        },
        {
          "assignment": "Unit 1 MC Quiz",
          "category": "Minor Grades",
          "dateAssigned": "",
          "dateDue": "01/21/2022",
          "score": "",
          "totalPoints": "100.00"
        },
        {
          "assignment": "Unit 1 Concept Application & Argument FRQ Practice",
          "category": "Minor Grades",
          "dateAssigned": "",
          "dateDue": "01/14/2022",
          "score": "",
          "totalPoints": "100.00"
        }
      ]
    }

  ]
}]

我需要将许多值用于完成块内的代码，所以我需要它们是浮点数而不是字符串。 如何将成绩、体重和学分等值更改为浮点值而不是字符串值？

完成块：

getData{ (studentData) in
          
        }

Answer 1

Please go to your model class and try to customised  the init() to convert `String` into `Float` values.
--------------------------------------------------------------------------
Note : 1. please do with CodingKeys
       2. add all keys which you want to Parse.

class CurrentClasses: Codable{
    var grade : Float
    var weight : Float
    var credits : Float

    private enum CodingKeys : String, CodingKey { 
    case grade,weight,credits 
}
    required init(from decoder: Decoder) throws {
        let container = try decoder.container(keyedBy: CodingKeys.self)
        let gradeString: String = try container.decode(String.self, forKey: .grade)
        self.grade = Float(gradeString)
        let weightString: String = try container.decode(String.self, forKey: .weight)
        self.weight = Float(weightString)
    }
}