Question

如何使用for循环和引用运算符在数组中循环？

private func setupLayout() {
    view.addSubview(imageView)
    view.addSubview(titleLabel)

    // *** imageView ***
    if #available(iOS 11.0, *) {
        imageView.topAnchor.constraint(equalTo: view.safeAreaLayoutGuide.topAnchor, constant: 116).isActive = true
    } else {
        imageView.topAnchor.constraint(equalTo: view.topAnchor, constant: 116).isActive = true
    }
    imageView.rightAnchor.constraint(equalTo: view.rightAnchor).isActive = true
    imageView.leftAnchor.constraint(equalTo: view.leftAnchor).isActive = true
    imageView.heightAnchor.constraint(equalToConstant: 224).isActive = true

    // *** titleLabel ***
    titleLabel.topAnchor.constraint(equalTo: imageView.bottomAnchor, constant: 25).isActive = true
    titleLabel.rightAnchor.constraint(equalTo: view.rightAnchor, constant: -28).isActive = true
    titleLabel.leftAnchor.constraint(equalTo: view.leftAnchor, constant: 28).isActive = true
}

我应该在哪里插入i？

这些是结构：

for (i = 0; i < university->size; i++)
    {
        if (university->arr->MarkA <= 100)
        {
            sum += university->arr->MarkA;
            count++;
        }

我使用了一个函数来创建大学数组

typedef struct Student
{
    char *name;
    long ID;
    int MarkA, MarkB, HW;
}stud;

typedef struct University
{
    stud *arr;
    int size;
}Uni;

在主函数中，我调用了上述函数以在此结构上工作

void build_Uni(FILE* in, Uni* university)
{
    int i = 0;
    stud temp;
    char Name[100];
    while (!feof(in))
    {
        fscanf(in, "%s%li%d%d%d", Name, &temp.ID, &temp.MarkA, &temp.MarkB, &temp.HW);
        i++;
    }
    university->size = i;
    rewind(in);
    university->arr = (stud*)malloc(university->size * sizeof(stud));
    if (university->arr == NULL) Get_Lost("Memory allocation failed!");
    else for (i = 0; i < university->size; i++)
        fill_Uni(in, university->arr + i);
}

void fill_Uni(FILE* in, stud* student)
{
    char Name[100];
    fscanf(in, "%s%li%d%d%d", Name, &student->ID, &student->MarkA, &student->MarkB, &student->HW);
    student->name = (char*)malloc((strlen(Name) + 1) * sizeof(char));
    if (student->name == NULL) Get_Lost("Error allocatig memory");
    strcpy(student->name, Name);
}

Answer 1

如何使用for循环和引用循环遍历数组运算符？

我认为您的意思是解引用运算符->，但引用和解引用与遍历数组无关。这就是您的for循环的目的。

我应该在哪里插入i？

此：

for (i = 0; i < university->size; i++)
{
        if (university->arr->MarkA <= 100)
        {
            sum += university->arr->MarkA;
            count++;
        }
}

应该是这样

for (i = 0; i < university->size; i++)
{
        if (university->arr[i].MarkA <= 100)
        {
            sum += university->arr[i].MarkA;
            count++;
        }
}

Answer 2

关于原始问题，您应该按以下方式访问它：

University university;
 ...  
for (i = 0; i < university.size; i++) {

    if (university.arr[i].MarkA <= 100)
    {
        sum += university.arr[i].MarkA;
        count++;
    }
    ...
}

但是，如果university的类型为University*，则代码会稍有变化，因为您必须使用运算符->来访问university成员：

for (i = 0; i < university->size; i++) {

    if (university->arr[i].MarkA <= 100)
    {
        sum += university->arr[i].MarkA;
        count++;
    }
    ...
}

使用引用运算符访问结构层

2 个答案: