# 概述

在Swift中提供了三种基本的集合类型。

* Array ： 有序的可重复的
* Set ： 无序的不可重复的
* Dictionary ： 无序的不可重复的字典

![](https://docs.swift.org/swift-book/_images/CollectionTypes_intro_2x.png)

## 集合类型的可变性

如果集合类型被赋予给常量，集合类型则不可更改，不能增加删除元素，也不能修改元素；

如果集合类型赋予给变量，则可以修改。


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