我正在尝试从以下JSON对象 data.json中检索信息：
{
"status": "ok",
"feed": {
"title": "NOS Nieuws",
},
"items": [
{
"title": "Test Title",
"description": "Test description",
"enclosure": {
"link": "https://examplelink.com/1008x567.jpg",
"type": "image/jpeg"
},
"categories": []
},
{
"title": "Test Title 2",
"description": "Test 2",
"enclosure": {
"link": "link": "https://examplelink.com/1008x567.jpg",
"type": "image/jpeg"
},
"categories": []
}
]
}
因此，我想遍历此JSON对象以显示所有可用项及其相应的标题，描述和附件链接。
我知道我可以通过以下方式分别访问它们：
const items = data.items;
const title = items.title;
const url = items.enclosure.link;
通常，我会进行for循环并遍历data.items [i]。但是，由于这是一个React对象，而不是数组，因此它的工作方式有所不同。
我当前的代码：
class Feed extends Component {
render() {
const items = data.items[0];
const title = items.title;
const url = items.enclosure.link;
const description = items.description;
const feed = [
{
url: url,
title: title,
description: description
}
];
return (
<div className="feed">
<h1>Newsfeed</h1>
<div className="columns is-multiline">
{feed.map(article => (
<div className="column is-one-third">
<NewsCard
article={article}
title={items.title}
description={items.description}
/>
</div>
))}
</div>
</div>
);
}
}
现在它仅显示对象的第一个条目（因为它具有const items = data.items [0]）如何遍历data.json并在NewsCard组件中显示其内容？我知道每个孩子都应该有一个独特的“钥匙”道具，但这就是我被困住的地方。
答案 0 :(得分：1)
我想遍历此JSON对象以显示所有可用的 项目及其相应的标题，描述和附件链接
然后不要这样做：
const items = data.items[0];
尝试一下：
const items = data.items;
然后，您可以使用map函数，如下所示：
items.map(item => (
<div className="column is-one-third">
<NewsCard
article={item.enclosure.link}
title={item.title}
description={item.description}
/>
</div>
));
答案 1 :(得分：0)
class ResizablePixmap(QLabel):
def __init__(self, bytes_image):
QLabel.__init__(self)
self.setSizePolicy(QSizePolicy.Ignored, QSizePolicy.Ignored)
self.setAlignment(Qt.AlignCenter)
self.setStyleSheet("background-color: #ffffff;")
self.update_pixmap(bytes_image)
def update_pixmap(self, bytes_image):
self.bytes_image_edit = bytes_image
self.current_pixmap = self._bytes2pixmap(bytes_image)
def scale(self, fromResize=False):
# use a single central method for scaling; there's no need to call it upon
# creation and also resize() won't work anyway in a layout
self.setPixmap(self.current_pixmap.scaled(self.width(), self.height(),
Qt.KeepAspectRatio, Qt.SmoothTransformation))
def resizeEvent(self, event):
super(ResizablePixmap, self).resizeEvent(event)
self.scale(True)
@staticmethod
def _bytes2pixmap(raw_image):
image = QImage()
image.loadFromData(raw_image)
return QPixmap(image)
class SelectablePixmap(ResizablePixmap):
selectionActive = pyqtSignal(bool)
def __init__(self, bytes_image):
super().__init__(bytes_image)
# activate mouse tracking to change cursor on rubberband hover
self.setMouseTracking(True)
self.currentQRubberBand = None
self.rubber_band_offset = None
self.moveDirection = 0
def create_selection(self, pos):
if self.currentQRubberBand:
self.cancel_selection()
self.currentQRubberBand = QRubberBand(QRubberBand.Rectangle, self)
self.currentQRubberBand.setStyle(QStyleFactory.create("Fusion"))
self.currentQRubberBand.setGeometry(pos.x(), pos.y(), 1, 1)
self.currentQRubberBand.show()
self.originQPoint = pos
self.currentQRubberBand.installEventFilter(self)
def cancel_selection(self):
self.currentQRubberBand.hide()
self.currentQRubberBand.deleteLater()
self.currentQRubberBand = None
self.originQPoint = None
self.selectionActive.emit(False)
def scale(self, fromResize=False):
if fromResize and self.currentQRubberBand:
# keep data for rubber resizing, before scaling
oldPixmapRect = self.pixmap().rect()
oldOrigin = self.currentQRubberBand.pos() - self.pixmapRect.topLeft()
super(SelectablePixmap, self).scale()
# assuming that you always align the image in the center, get the current
# pixmap rect and move the rectangle center to the current geometry
self.pixmapRect = self.pixmap().rect()
self.pixmapRect.moveCenter(self.rect().center())
if fromResize and self.currentQRubberBand:
# find the new size ratio based on the previous
xRatio = self.pixmapRect.width() / oldPixmapRect.width()
yRatio = self.pixmapRect.height() / oldPixmapRect.height()
# create a new geometry using 0-rounding for improved accuracy
self.currentQRubberBand.setGeometry(
round(oldOrigin.x() * xRatio, 0) + self.pixmapRect.x(),
round(oldOrigin.y() * yRatio + self.pixmapRect.y(), 0),
round(self.currentQRubberBand.width() * xRatio, 0),
round(self.currentQRubberBand.height() * yRatio, 0))
def updateMargins(self):
# whenever the rubber rectangle geometry changes, create virtual
# rectangles for corners and sides to ease up mouse event checking
rect = self.currentQRubberBand.geometry()
self.rubberTopLeft = QRect(rect.topLeft(), QSize(8, 8))
self.rubberTopRight = QRect(rect.topRight(), QSize(-8, 8)).normalized()
self.rubberBottomRight = QRect(rect.bottomRight(), QSize(-8, -8)).normalized()
self.rubberBottomLeft = QRect(rect.bottomLeft(), QSize(8, -8)).normalized()
self.rubberLeft = QRect(self.rubberTopLeft.bottomLeft(), self.rubberBottomLeft.topRight())
self.rubberTop = QRect(self.rubberTopLeft.topRight(), self.rubberTopRight.bottomLeft())
self.rubberRight = QRect(self.rubberTopRight.bottomLeft(), self.rubberBottomRight.topRight())
self.rubberBottom = QRect(self.rubberBottomLeft.topRight(), self.rubberBottomRight.bottomLeft())
self.rubberInnerRect = QRect(self.rubberTop.bottomLeft(), self.rubberBottom.topRight())
def eventFilter(self, source, event):
if event.type() in (QEvent.Resize, QEvent.Move):
self.updateMargins()
return super(SelectablePixmap, self).eventFilter(source, event)
def mousePressEvent(self, event):
pos = event.pos()
if not self.currentQRubberBand or not pos in self.currentQRubberBand.geometry():
if pos not in self.pixmapRect:
self.originQPoint = None
return
self.create_selection(pos)
elif pos in self.rubberTopLeft:
self.originQPoint = self.currentQRubberBand.geometry().bottomRight()
elif pos in self.rubberTopRight:
self.originQPoint = self.currentQRubberBand.geometry().bottomLeft()
elif pos in self.rubberBottomRight:
self.originQPoint = self.currentQRubberBand.geometry().topLeft()
elif pos in self.rubberBottomLeft:
self.originQPoint = self.currentQRubberBand.geometry().topRight()
elif pos in self.rubberTop:
self.originQPoint = self.currentQRubberBand.geometry().bottomLeft()
self.moveDirection = Qt.Vertical
elif pos in self.rubberBottom:
self.originQPoint = self.currentQRubberBand.geometry().topLeft()
self.moveDirection = Qt.Vertical
elif pos in self.rubberLeft:
self.originQPoint = self.currentQRubberBand.geometry().topRight()
self.moveDirection = Qt.Horizontal
elif pos in self.rubberRight:
self.originQPoint = self.currentQRubberBand.geometry().topLeft()
self.moveDirection = Qt.Horizontal
else:
self.rubber_band_offset = pos - self.currentQRubberBand.pos()
def mouseMoveEvent(self, event):
pos = event.pos()
if event.buttons() == Qt.NoButton and self.currentQRubberBand:
if pos in self.rubberTopLeft or pos in self.rubberBottomRight:
self.setCursor(Qt.SizeFDiagCursor)
elif pos in self.rubberTopRight or pos in self.rubberBottomLeft:
self.setCursor(Qt.SizeBDiagCursor)
elif pos in self.rubberLeft or pos in self.rubberRight:
self.setCursor(Qt.SizeHorCursor)
elif pos in self.rubberTop or pos in self.rubberBottom:
self.setCursor(Qt.SizeVerCursor)
elif pos in self.rubberInnerRect:
self.setCursor(Qt.SizeAllCursor)
else:
self.unsetCursor()
elif event.buttons():
if self.rubber_band_offset:
target = pos - self.rubber_band_offset
rect = QRect(target, self.currentQRubberBand.size())
# limit positioning of the selection to the image rectangle
if rect.x() < self.pixmapRect.x():
rect.moveLeft(self.pixmapRect.x())
elif rect.right() > self.pixmapRect.right():
rect.moveRight(self.pixmapRect.right())
if rect.y() < self.pixmapRect.y():
rect.moveTop(self.pixmapRect.y())
elif rect.bottom() > self.pixmapRect.bottom():
rect.moveBottom(self.pixmapRect.bottom())
self.currentQRubberBand.setGeometry(rect)
elif self.originQPoint:
if self.moveDirection == Qt.Vertical:
# keep the X fixed to the current right, so that only the
# vertical position is changed
pos.setX(self.currentQRubberBand.geometry().right())
else:
# limit the X to the pixmapRect extent
if pos.x() < self.pixmapRect.x():
pos.setX(self.pixmapRect.x())
elif pos.x() > self.pixmapRect.right():
pos.setX(self.pixmapRect.right())
if self.moveDirection == Qt.Horizontal:
# same as before, but for the Y position
pos.setY(self.currentQRubberBand.geometry().bottom())
else:
# limit the Y to the pixmapRect extent
if pos.y() < self.pixmapRect.y():
pos.setY(self.pixmapRect.y())
elif pos.y() > self.pixmapRect.bottom():
pos.setY(self.pixmapRect.bottom())
rect = QRect(self.originQPoint, pos)
self.currentQRubberBand.setGeometry(rect.normalized())
def mouseReleaseEvent(self, event):
self.rubber_band_offset = None
self.originQPoint = None
self.moveDirection = 0
尝试这种方式
答案 2 :(得分：0)
您可以这样做。
class Feed extends Component {
render() {
let newsCards = data.items.map(item => {
<div className="column is-one-third">
<NewsCard
article={item}
title={item.title}
description={item.description}
/>
</div>
});
return (
<div className="feed">
<h1>Newsfeed</h1>
<div className="columns is-multiline">
{newsCards}
</div>
</div>
);
}
}