Question

我正在尝试比较对象的多个属性，但我的代码只能比较度属性。在Visual Studio中进行调试时，似乎我的代码完全缺少else语句。我会很感激任何提示。

//define model
$scope.tobeDeleted = {}; //then place deleted property here
//you could easily access `$scope.tobeDeleted.deletedId` inside a controller

Answer 1

您的问题的第一个答案（为什么else部分永远不会被执行）已经得到回答，也就是说，没有第三种情况可能是1或not 1。

如果您尝试按不同的属性进行排序，例如，首先我们要按度数排序，然后按fName排序然后我们可以实现IComparer -

class Student : IComparer<Student>{

    /*
    codes
   */


    public int Compare(Student student1, Student student2)
   {
          if(student1.deg.Equals(student2.deg))  //if both degrees are same
          {
              return string.Compare(student1.fName , student2.fName); // then compare fName
          }
          else
              return string.Compare(student1.deg , student2.deg);


   }
}

Answer 2

在您的代码中

if (this.deg.CompareTo(newStudent.deg) == 1)
{
    // do something
}
else if (this.deg.CompareTo(newStudent.deg) != 1)
{
    // do something
}
else 
{
    // do something
}

永远不会达到

else语句，因为结果可以等于1。而且你只检查'deg'值。例如，您可以检查它们是否相同：

public int CompareTo(object obj)
{
    if (obj == null)
    {
        return -1;
    }
    Student newStudent = obj as Student;
    // are equal
    if (deg.CompareTo(newStudent.deg) == 0 && 
        gra.CompareTo(newStudent.gra) == 0 &&
        lName.CompareTo(newStudent.lName) == 0 &&
        fName.CompareTo(newStudent.fName) == 0)
    {
        return 0;
    }
    else
    {
        return 1;
    }
}

Answer 3

如果this.deg.CompareTo(newStudent.deg) == 1则返回1，如果this.deg.CompareTo(newStudent.deg) != 1则返回-1。由于比较要么是，要么等于1，你永远不会到达其余的。

因此，您的代码应如下所示：

partial class Student : IComparable, IComparable<Student>
{
    public int CompareTo(object obj)
    {
        if (obj != null && obj.GetType() != GetType())
        {
            // From https://msdn.microsoft.com/en-us/library/system.icomparable.compareto(v=vs.110).aspx#Remarks
            // The parameter, obj, must be the same type as the class or value type that implements this interface; otherwise, an ArgumentException is thrown.
            throw new ArgumentException(string.Format("Object must be of type {0}", GetType()));
        }
        return CompareTo((Student)obj);
    }

    public int CompareTo(Student newStudent)
    {
        if (object.ReferenceEquals(this, newStudent))
            return 0;
        else if (newStudent == null)
            // From https://msdn.microsoft.com/en-us/library/43hc6wht(v=vs.110).aspx#Remarks
            // By definition, any object compares greater than null, and two null references compare equal to each other.
            return 1;

        var cmp = this.deg.CompareTo(newStudent.deg);
        if (cmp != 0)
            return cmp;

        cmp = this.fName.CompareTo(newStudent.fName);
        if (cmp != 0)
            return cmp;

        // Compare additional members as required, return the first nonzero member comparison.

        // Finally return 0 if all member comparisons returned 0.
        return 0;
    }
}

注意：

如果您要实施IComparable，您还应该IComparable<Student>中解释的原因实施IComparable and IComparable<T>。
由于IComparable是由可以排序或排序的类型实现，如IComparable<T>.CompareTo Method (T): Notes to Implementers所述，您应确保您的比较方法为{{3} }。通过连续调用CompareTo成员的Student方法，并返回第一个非零值，您可以确保是这种情况。

IComparable CompareTo（），如何比较多个对象属性？

3 个答案: