From a5e2d57894db328cf36bdf6d68d8b215ece4cfd7 Mon Sep 17 00:00:00 2001
From: chenos <chenlinxh@gmail.com>
Date: Mon, 29 Nov 2021 10:00:42 +0800
Subject: [PATCH] docs: update api doc

---
 docs/reference/database.md | 47 ++++++++++++++++++++++++++++++++++++++
 1 file changed, 47 insertions(+)

diff --git a/docs/reference/database.md b/docs/reference/database.md
index 37208817b6..1678056612 100644
--- a/docs/reference/database.md
+++ b/docs/reference/database.md
@@ -194,6 +194,8 @@ interface ImportOptions {
   // @default ['js', 'ts', 'json']
   extensions?: string[];
 }
+// 为了配合 db.import()，提供了一个 extend 方法，用于扩展已有 collection 配置
+function extend(collectionOptions: CollectionOptions, mergeOptions?: MergeOptions) {}
 ```
 
 ##### Examples
@@ -244,6 +246,51 @@ extend({
 });
 ```
 
+extend 可以自定义 merge 规则（[deepmerge](https://www.npmjs.com/package/deepmerge#options)），如：
+
+```ts
+extend({
+  name: 'demos',
+  actions: [
+    {
+      name: 'list',
+    },
+  ],
+}, {
+  arrayMerge: (t, s) => t.concat(s),
+})
+```
+
+备注：extend 的 fields、hooks 等 array 参数，默认都是 concat 规则，string 参数是覆盖，如：
+
+```ts
+{
+  name: 'tests',
+  repository: 'TestRepository1',
+  fields: [
+    { type: 'string', name: 'name1' },
+  ],
+}
+
+extend({
+  name: 'tests',
+  repository: 'TestRepository2',
+  fields: [
+    { type: 'string', name: 'name2' },
+  ],
+});
+
+// 等同于
+{
+  name: 'tests',
+  repository: 'TestRepository2',
+  fields: [
+    { type: 'string', name: 'name1' },
+    { type: 'string', name: 'name2' },
+  ],
+}
+```
+
 ## `db.on()`
 
 ##### Definition