Question

我已经坚持了一段时间。

这是我的redux-state的一部分

state: {

  teachers: [
    { teacherId: 'ttt1', teacherName: 'Susan', isCool: true, teachesAt: 'sss1'},
    { teacherId: 'ttt2', teacherName: 'Karen', isCool: false, teachesAt: 'sss2'},
    { teacherId: 'ttt3', teacherName: 'Bob', isCool: true, teachesAt: 'sss3'},
    { teacherId: 'ttt4', teacherName: 'Mike', isCool: false, teachesAt: 'sss1'},
  ],

  schools: [
    { schoolId: 'sss1', schoolName: 'Washington'},
    { schoolId: 'sss2', schoolName: 'Lincoln'},
    { schoolId: 'sss3', schoolName: 'Jefferson'},
  ],

  students: [
    { schoolIdEnrolled: 'sss1', studentName: 'Billy'},
    { schoolIdEnrolled: 'sss1', studentName: 'Steven'},
    { schoolIdEnrolled: 'sss2', studentName: 'Bobby'},
    { schoolIdEnrolled: 'sss3', studentName: 'Mikey'},
    { schoolIdEnrolled: 'sss3', studentName: 'Sally'},
    { schoolIdEnrolled: 'sss3', studentName: 'Cindy'},
    { schoolIdEnrolled: 'sss3', studentName: 'Mandy'},
  ],

  classes: [...],

}

任何人都可以梦想一种方式，以便在我的渲染方法中 React Component I可以遍历我的学校并计算数字每个学校的'coolTeachers'和'studentCount'？这是用例重新选择？

我的桌子必须是这样的：

学校______＃冷却教师_______学生

华盛顿__________ 1 _______________________ 2

林肯______________ 0 _______________________ 1

杰弗逊____________ 1 _______________________ 4

Answer 1

这是Array.prototype.reduce的经典用例：

public static void main(String[] args)
{
    EventQueue.invokeLater(new Runnable()
    {
        @Override
        public void run()
        {
            new Calculator();

        }
    });
     //TODO code application logic here
}


JPanel[] row = new JPanel[5];
JButton[] button = new JButton[19];
String[] buttonString = {"7", "8", "9", "+",
                         "4", "5", "6", "-",
                         "1", "2", "3", "*",
                         ".", "/", "C","Sqrt",
                         "+/-", "=", "0"};

int[] dimW = {300,45,100,90};
int[] dimH = {35, 40};
Dimension displayDimension = new Dimension(dimW[0], dimH[0]);
Dimension regularDimension = new Dimension(dimW[1], dimH[1]);
Dimension rColumnDimension = new Dimension(dimW[2], dimH[1]);
Dimension zeroButDimension = new Dimension(dimW[3], dimH[1]);
boolean[] function = new boolean[4];
double[] temporary = {0, 0};
JTextArea display = new JTextArea(1,20);
Font font = new Font("Times new Roman", Font.BOLD, 12);

Calculator(){
    super("Calculator");
    setDesign();
    setSize(400, 400);
    setResizable(false);
    setDefaultCloseOperation(EXIT_ON_CLOSE);
    GridLayout grid = new GridLayout (5,5);
    setLayout(grid);
     setVisible(true);

    for(int i = 0; i < 19; i++)
        function[i] = false;

    FlowLayout f1 = new FlowLayout(FlowLayout.CENTER);
    FlowLayout f2 = new FlowLayout(FlowLayout.CENTER,1,1);
    for(int i = 0; i < 5; i++)
        row[i] = new JPanel();
    row[0].setLayout(f1);
    for(int i = 1; i < 5; i++)
        row[i].setLayout(f2);
    for(int i = 0; i < 19; i++){

        button[i] = new JButton();
        button[i].setText(buttonString[i]);
        button[i].setFont(font);
        button[i].addActionListener(this);
    }

    display.setFont(font);
    display.setEditable(false);
    display.setComponentOrientation(ComponentOrientation.RIGHT_TO_LEFT);
    display.setPreferredSize(displayDimension);
    for(int i = 0; i < 14; i++)
        button[i].setPreferredSize(regularDimension);
    for(int i = 14; i < 18; i++)
        button[i].setPreferredSize(rColumnDimension);
    button[18].setPreferredSize(zeroButDimension);

    row[0].add(display);
    add(row[0]);

    for(int i = 0; i < 4; i++)
        row[1].add(button[i]);
    row[1].add(button[14]);
    add(row[1]);
    for(int i = 4; i < 8; i++)
        row[2].add(button[i]);
    row[2].add(button[15]);
    add(row[2]);

    for(int i = 8; i < 12; i++)
        row[3].add(button[i]);
    row[3].add(button[16]);
    add(row[3]);

    row[4].add(button[18]);
    for(int i = 12; i < 14; i++)
        row[4].add(button[i]);
    row[4].add(button[17]);
    add(row[4]);     
}

public void clear() {
    try {
        display.setText("");
        for (int i = 0; i < 4; i++)
            function[i] = false;
        for(int i = 0; i < 2; i++)
            temporary[i] = 0;
    } catch(NullPointerException e) {
    }
}

public void getSqrt() {
    try {
        double value = Math.sqrt(Double.parseDouble(display.getText()));
        display.setText(Double.toString(value));
    } 
    catch(NumberFormatException e) {
    }
}

public void getPosNeg() {
    try {
        double value = Double.parseDouble(display.getText());
        if(value !=0) {
            value = value * (-1);
            display.setText(Double.toString(value));
        }
        else {
        }
    } catch(NumberFormatException e) {
    }
}

public void getResult() {
    double result = 0;
    temporary[1] = Double.parseDouble(display.getText());
    String temp0 = Double.toString(temporary[0]);
    String temp1 = Double.toString(temporary[1]);
    try {
        if(temp0.contains("-")) {
            String[] temp00 = temp0.split("-", 2);
            temporary[0] = (Double.parseDouble(temp00[1]) * -1);
        }
        if(temp1.contains("-")) {
            String[] temp11 = temp1.split("-", 2);
            temporary[1] = (Double.parseDouble(temp11[1]) * -1);
        }
    }
    catch(ArrayIndexOutOfBoundsException e) {
    }
    try {
        if(function[2] == true)
            result = temporary[0] * temporary[1];
        else if(function[3] == true)
            result = temporary[0] / temporary[1];
        else if(function[0] == true)
            result = temporary[0] + temporary[1];
        else if(function[1] == true)
            result = temporary[0] - temporary[1];
        display.setText(Double.toString(result));
        for(int i = 0; i < 4; i++)
            function[i] = false;
    }
    catch(NumberFormatException e) {
    }
}

public final void setDesign(){
    try {
        UIManager.setLookAndFeel(
                "com.sun.java.swing.plaf.nimbus.NimbusLookAndFeel");
    } catch(Exception e) {
    }
}

public void actionPerformed(ActionEvent ae) {
   if(ae.getSource() == button[0])
       display.append("7");
   if(ae.getSource() == button[1])
       display.append("8");
   if(ae.getSource() == button[2])
       display.append("9");
   if(ae.getSource() == button[3]) {

       temporary[0] = Double.parseDouble(display.getText());
       function[0] = true;
       display.setText("");
   }
   if(ae.getSource() == button[4])
       display.append("4");
   if(ae.getSource() == button[5]);
   display.append("5");
   if(ae.getSource() == button[6])
       display.append("6");
   if(ae.getSource() == button[7]) {

       temporary[0] = Double.parseDouble(display.getText());
       function[1] = true;
       display.setText("");
   }
   if(ae.getSource() == button[8])
       display.append("1");
   if(ae.getSource() == button[9]);
   display.append("2");
   if(ae.getSource() == button[10]);
   display.append("3");
   if(ae.getSource() == button[11]) {

       temporary[0] = Double.parseDouble(display.getText());
       function[2] = true;
       display.setText("");
   }
   if(ae.getSource() == button[12])
       display.append(".");
   if(ae.getSource() == button[13]) {

       temporary[0] = Double.parseDouble(display.getText());
       function[3] = true;
       display.setText("");
   }
   if(ae.getSource() == button[14])
       clear();
   if(ae.getSource() == button[15])
       getSqrt();
   if(ae.getSource() == button[16])
       getPosNeg();
   if(ae.getSource() == button[17])
       getResult();
   if(ae.getSource() == button[18])
       display.append("0");
}

您可以使用reselect包装方法，但请记住它只会缓存最后一个输入参数。

Redux状态使用重新选择来导出相关数据

1 个答案: