文件大小限制

除了用户帐户icloud存储容量之外,文档不指定文档文件大小限制,也不指定核心数据存储限制.密钥值存储有一个限制,对于一个值(在一个值 – 密钥对中)是1Mb,这可能是一个问题,但是除非用户有足够的可用空间,否则它似乎可以存储大文件.

鉴于5gb默认金额并考虑到默认用户存储需求(照片,联系人,日历等),您可能会遇到与任何其他应用程序一样的文档和核心数据存储限制. file management for icloud页面提到了良好的应用行为：

Apps that take advantage of iCloud storage features should act
responsibly when storing data in there. The space available in each
user’s account is limited and is shared by all apps. In addition,
users can see how much space is consumed by a given app and choose to
delete documents and data associated with your app. For these reasons,
it is in your app’s interest to be responsible about what files you
store.

以编程方式检查可用空间

没有

上传/下载活动

文件上载和下载由OS处理.所有文件都存储在本地,它来自您请求/修改/保存文档的本地存储.从icloud基础页面：

When you adopt iCloud,the operating system initiates and manages
uploading and downloading of data for the devices attached to an
iCloud account. Your app does not directly communicate with iCloud
servers and,in most cases,does not invoke upload or download of
data.

有关键值存储集成的示例,请参阅此app coda教程,此核心数据存储集成的Tim Roadley教程或此文档存储集成的Ray Wenderlich教程.

编辑：Document-Based App Programming Guide for iOS提供了用于将文件移入/移出iCloud,上载和下载以及监视文件更改的代码片段.请参阅“从iCloud下载文档文件”和“将文档移动到iCloud存储”.