swift - 我的 for 循环出了什么问题 - 它没有达到最高等级

Question

我有一个 for 循环(在函数内部)，应该输出类(class)中的最高成绩。但它并没有在类取得“A”。为什么不呢？

我还预计我的数组索引会生成超出范围的错误，但我没有收到错误。我猜是幸运的，尽管我不确定为什么。

struct Student {
   let firstName: String
   let lastName: String
   let grade: String 
}

struct Classroom {
 let nameOfClass: String
 let students: [Student]

 func highGrade(students: [Student]) {
     var x: Int = 0

     for student in students {
        if students[x].grade < students[x + 1].grade {
            print(student.grade)
             x += 1
         }
         else {
             print("Nope")
         }
     }
 } }

let student1 = Student(firstName: "Keith", lastName: "Grimes", grade: "F")
let student2 = Student(firstName: "Debbie", lastName: "Grimes", grade: "A")
let student3 = Student(firstName: "Nicholas", lastName: "Grimes", grade: "C")

let class1 = Classroom(nameOfClass: "Swift", students: [student1, student2, student3])

class1.highGrade(students: [student1, student2, student3])

我正在尝试找出类三名学生中的最高成绩。

Answer 1

我更喜欢显式初始化程序在初始化时对学生进行排序，如下所示，

struct Classroom {
    let nameOfClass: String
    let students: [Student]

    init(_ className: String, students: [Student]) {
        self.nameOfClass = className
        self.students = students.sorted(by: { $0.grade < $1.grade })
    }
}

用法:

let student1 = Student(firstName: "Keith", lastName: "Grimes", grade: "F")
let student2 = Student(firstName: "Debbie", lastName: "Grimes", grade: "A")
let student3 = Student(firstName: "Nicholas", lastName: "Grimes", grade: "C")

let class1 = Classroom("Swift", students: [student1, student2, student3])
print(class1.students.first?.grade)
print(class1.students.first?.firstName)

输出:

Optional("A")
Optional("Debbie")