Question

我有一个错误对象的字典，我想将errorMessage属性连接成一个字符串，其中换行符作为字典中每个项目的分隔符。以下代码完成了这项工作，但我确信必须有更优雅的方式

var errorMessage = ""
var count = 1
for (_, error) in validator.errors {
    errorMessage += error.errorMessage + "\n"
    if count < validator.errors.count{
        errorMessage +=  "\n"             
    }
    count++
}

达到我想要做的最好的方法是什么？

Answer 1

像

这样的东西

public class FileSystemTreeCellRenderer implements TreeCellRenderer {
    protected Color foregroundColor = null;
    protected Color backgroundColor = null;
    protected Color selectionForegroundColor = null;
    protected Color selectionBackgroundColor = null;
    protected Map<Object, JLabel> labels = new HashMap<>();
    protected final Icon  folderSpecial;
    protected final Icon  folderOther;
    protected final Icon  fileSpecial;
    protected final Icon  fileOther;

    public FileSystemTreeCellRenderer() throws IOException {
        InputStream stream;
        BufferedImage image;

        stream = new FileInputStream("folder-special.png");
        image = ImageIO.read(stream);
        folderSpecial = new ImageIcon(image);
        stream.close();

        stream = new FileInputStream("folder-other.png");
        image = ImageIO.read(stream);
        folderOther = new ImageIcon(image);
        stream.close();

        stream = new FileInputStream("file-special.png");
        image = ImageIO.read(stream);
        fileSpecial = new ImageIcon(image);
        stream.close();

        stream = new FileInputStream("file-other.png");
        image = ImageIO.read(stream);
        fileOther = new ImageIcon(image);
        stream.close();
    }

    protected JLabel getLabelFor(Object object) {
        JLabel label = labels.get(object);
        if(label == null) {
            label = new JLabel();
            labels.put(object, label);
        }
        return label;
    }

    public Color getForegroundColor() {
        if (foregroundColor == null) return UIManager.getColor("Tree.textForeground");
        return foregroundColor;
    }

    public Color getBackgroundColor() {
        if (backgroundColor == null) return UIManager.getColor("Tree.textBackground");
        return backgroundColor;
    }

    public Color getSelectionForegroundColor() {
        if (selectionForegroundColor == null) return UIManager.getColor("Tree.selectionForeground");
        return selectionForegroundColor;
    }

    public Color getSelectionBackgroundColor() {
        if (selectionBackgroundColor == null) return UIManager.getColor("Tree.selectionBackground");
        return selectionBackgroundColor;
    }

    @Override
    public Component getTreeCellRendererComponent(JTree tree, Object value, boolean selected, boolean expanded, boolean leaf, int row, boolean hasFocus) {
        JLabel label = getLabelFor(value);
        label.setText(Objects.toString(value, ""));
        label.setOpaque(true);
        label.setBackground(selected ? getSelectionBackgroundColor() : getBackgroundColor());
        label.setForeground(selected ? getSelectionForegroundColor() : getForegroundColor());
        label.setEnabled(tree.isEnabled());
        label.setComponentOrientation(tree.getComponentOrientation());

        if (value instanceof File) {
            Icon icon = null;
            File file = (File) value;

            if (file.isDirectory()) {
                if (file.getName().endsWith("-special")) {
                    icon = folderSpecial;
                } else {
                    icon = folderOther;
                }
            } else if (file.isFile()) {
                if (file.getName().endsWith(".special")) {
                    icon = fileSpecial;
                } else {
                    icon = fileOther;
                }
            }

            label.setIcon(icon);
        }

        return label;
    }
}

应该是技巧（不是编译器检查，可能有拼写错误但是你应该明白这一点。

let errorMessage = validator.errors.values.map({$0.errorMessage}).joinWithSeparator("\n")给出（序列）所有字典值。
validator.errors.values将每个值.map({$0.errorMessage})映射到error，结果是一个数组。
error.errorMessage将数组元素连接起来插入换行符。

Swift：使用换行符将字典转换为字符串

1 个答案: