https://facebook.github.io/relay/graphql/objectidentification.htm非常明确#include <gst/gst.h>
/* Structure to contain all our information, so we can pass it to callbacks */
typedef struct _CustomData {
GstElement *pipeline;
GstElement *source;
GstElement *convert;
GstElement *sink;
GstElement *encode;
} CustomData;
int main(int argc, char *argv[]) {
CustomData data;
GstBus *bus;
GstMessage *msg;
GstStateChangeReturn ret;
gboolean terminate = FALSE;
/* Initialize GStreamer */
gst_init (&argc, &argv);
/* Create the elements */
data.source = gst_element_factory_make ("videotestsrc", "source");
data.convert = gst_element_factory_make ("ffmpegcolorspace", "convert");
data.encode = gst_element_factory_make ("ffenc_pgm", "encode");
data.sink = gst_element_factory_make ("multifilesink", "sink");
/* Create the empty pipeline */
data.pipeline = gst_pipeline_new ("test-pipeline");
if (!data.pipeline || !data.source || !data.convert || !data.sink) {
g_printerr ("Not all elements could be created.\n");
return -1;
}
/* Build the pipeline. Note that we are NOT linking the source at this
* point. We will do it later. */
gst_bin_add_many (GST_BIN (data.pipeline), data.source, data.convert , data.encode, data.sink, NULL);
if (!gst_element_link_many (data.source, data.convert, data.encode, data.sink, NULL)) {
g_printerr ("Elements could not be linked.\n");
gst_object_unref (data.pipeline);
return -1;
}
/* Modify the source's properties */
g_object_set (data.source, "pattern", 0, NULL);
g_object_set (data.source, "num-buffers", 9, NULL);
g_object_set(data.sink, "location", "frame%05d.pgm", NULL);
/* Start playing */
ret = gst_element_set_state (data.pipeline, GST_STATE_PLAYING);
if (ret == GST_STATE_CHANGE_FAILURE) {
g_printerr ("Unable to set the pipeline to the playing state.\n");
gst_object_unref (data.pipeline);
return -1;
}
/* Wait until error or EOS */
bus = gst_element_get_bus (data.pipeline);
msg = gst_bus_timed_pop_filtered (bus, GST_CLOCK_TIME_NONE, GST_MESSAGE_ERROR | GST_MESSAGE_EOS);
/* Parse message */
if (msg != NULL) {
GError *err;
gchar *debug_info;
switch (GST_MESSAGE_TYPE (msg)) {
case GST_MESSAGE_ERROR:
gst_message_parse_error (msg, &err, &debug_info);
g_printerr ("Error received from element %s: %s\n", GST_OBJECT_NAME (msg->src), err->message);
g_printerr ("Debugging information: %s\n", debug_info ? debug_info : "none");
g_clear_error (&err);
g_free (debug_info);
break;
case GST_MESSAGE_EOS:
g_print ("End-Of-Stream reached.\n");
break;
default:
/* We should not reach here because we only asked for ERRORs and EOS */
g_printerr ("Unexpected message received.\n");
break;
}
gst_message_unref (msg);
}
/* Free resources */
gst_object_unref (bus);
gst_element_set_state (data.pipeline, GST_STATE_NULL);
gst_object_unref (data.pipeline);
return 0;
}
是什么以及它的行为方式，但它并没有指定哪些对象必须实现它，或者如果你的对象没有实现的后果是什么？实现它。有哪些功能不起作用？这些物体完全被忽略了吗？并非现有规范中的所有对象（例如Node）都实现了它，因此它显然不是普遍要求的，但pageInfo有点特殊情况。
答案 0 :(得分：4)
另一种思考Node接口的方法是实现它的对象是 refetchable 。可反复性有效地意味着一个对象具有一个ID，我可以用它来识别对象并检索它;按照惯例，这些ID通常是不透明的，但是将包含类型信息和该类型中的标识符（例如，字符串的Base-64编码，如“Account：1234”）。
Relay将以两种方式利用可再融资性：
QWNjb3VudDoxMjM0标识的对象的某些数据（例如，name和address字段），那么您导航到我们显示一些其他字段（location，createdAt）的视图，然后Relay可以创建一个“重新获取”节点但只请求丢失字段的最小查询。Node接口来填充缺少的数据（例如：通过某些导航组合，您可能拥有视图中某些项目的完整信息，但需要为范围内的某些项填写location，或者您可以通过变异修改连接中的项目）。因此，在基本分页中，Relay通常最终会进行first + after查询以扩展连接，但如果您在真实应用中检查其网络流量，您还会看到它会生成{{ 1}}查询连接中的项目。所以是的，node没有实现pageInfo你是对的，这样做是没有意义的。