diff --git a/dev/hook.md b/dev/hook.md
index 8dc552b6..ae197313 100644
--- a/dev/hook.md
+++ b/dev/hook.md
@@ -13,9 +13,26 @@ export async function apply(ctx: Context) {
     // RecordDetail 为需要捕获的路由名
     // #get 表示仅捕获 GET 请求，若无此后缀表示捕获该路由的所有请求
     ctx.on('handler/after/RecordDetail#get', (h) => { // handler 系列钩子的一参数为对应的 Handler 实例
+        // 不允许查看 24 小时以前的提交记录
         if (h.rdoc._id.getTimestamp() < new Date(Date.now() - Time.day)) {
             h.rdoc.code = '';
         }
     });
 }
 ```
+
+```ts
+import { Context } from 'hydrooj';
+
+async function getAnnounce(domainId: string, limit = 5) {
+    // 获取公告...
+    return adocs;
+}
+
+export async function apply(ctx: Context) {
+    ctx.withHandlerClass('HomeHandler', (HomeHandler) => {
+        // 修改 HomeHandler 中的一个方法（添加公告）
+        HomeHandler.prototype.getAnnounce = getAnnounce;
+    });
+}
+```
\ No newline at end of file
diff --git a/docs/user/problem-create.md b/docs/user/problem-create.md
index 9ecc3e29..ea8cc2b3 100644
--- a/docs/user/problem-create.md
+++ b/docs/user/problem-create.md
@@ -199,15 +199,14 @@ int main(int argc, char* argv[]) {
     rnd.setSeed(time(NULL));
     int a = rnd.next(1000);
     int b = rnd.next(1000);
-    int d = a+b;
     // 本程序的输出将作为用户程序的输入
     cout << a << " " << b << endl;
     int c;
     // 用户程序的最后输出将作为本程序的输入
     cin >> c;
     //对比用户结果和预期结果
-    if (a+b != ans)
-        quitf(_wa, "%d + %d expected %d, found %d", a, b,d,c);   //输出错误的具体信息,便于做题者调试
+    if (a+b != c)
+        quitf(_wa, "%d + %d expected %d, found %d", a, b, a+b, c);   //输出错误的具体信息,便于做题者调试
     else
         quitf(_ok, "answer of %d +  %d is %d",a,b,c);
 }