什么是Universal Links?
在iOS9之前，对于从各种从浏览器、Safari中唤醒APP的需求，我们通常只能使用scheme。但是这种方式需要提前判断系统中是否安装了能够响应此scheme的app。
Universal Links是iOS9推出的一项功能，你的应用如果iOS设备上已经安装了你的app可以通过传统的HTTP链接来启动APP，iOS设备上没有安装你的app来打开网页。
官方的说明文档 怎么使用Universal Links。
1.先决条件：你必须有一个域名,且这个域名需要支持https。
2.需要在开发者中心做配置：找到对应的App ID，在Application Services列表里有Associated Domains一条，把它变为Enabled就可以了。
3.打开工程配置中的Associated Domains，在其中的Domains中填入你想支持的域名，必须以applinks:为前缀。
**4.创建一个内容为json格式的文件，app安装后，app从我们在项目中填入的域名请求这个文件。这个文件名必须为apple-app-site-association，没有后缀名，文件内容大概是这样子：
ios 12及其以前**
{
"applinks": {
"apps": [],
"details": [
{
"appID": "ABCDE12345.com.example.app",
"paths": [ "/buy/*", "NOT /help/website/*", "/help/*" ]
}
{
"appID": "ABCDE12345.com.example.app2",
"paths": [ "/buy/*", "NOT /help/website/*", "/help/*" ]
}
]
},
"webcredentials": {
"apps": [ "ABCDE12345.com.example.app" ]
}
}
ios13开始变了（有点坑）
{
"applinks": {
"details": [
{
"appIDs": [ "ABCDE12345.com.example.app", "ABCDE12345.com.example.app2" ],
"components": [
{
"#": "no_universal_links",
"exclude": true,
"comment": "Matches any URL whose fragment equals no_universal_links and instructs the system not to open it as a universal link"
},
{
"/": "/buy/*",
"comment": "Matches any URL whose path starts with /buy/"
},
{
"/": "/help/website/*",
"exclude": true,
"comment": "Matches any URL whose path starts with /help/website/ and instructs the system not to open it as a universal link"
}
{
"/": "/help/*",
"?": { "articleNumber": "????" },
"comment": "Matches any URL whose path starts with /help/ and which has a query item with name 'articleNumber' and a value of exactly 4 characters"
}
]
}
]
},
"webcredentials": {
"apps": [ "ABCDE12345.com.example.app" ]
}
}
- appID：组成方式是 teamId.yourapp’s bundle identifier。如上面的 9JA89QQLNQ就是teamId。登陆开发者中心，在Account - Membership里面可以找到Team ID
-paths：设定你的app支持的路径列表，只有这些指定的路径的链接，才能被app所处理。星号的写法代表了可识别域名下所有链接
5. 上传该文件到你的域名所对应的根目录或者.well-known目录下，这是为了苹果能获取到你上传的文件。上传完后,自己先访问一下,看看是否能够获取到，当你在浏览器中输入这个文件链接后，应该是直接下载apple-app-site-association文件。
在safari中输入一下两个链接能下载到上述的json文件
(https://你的域名/.well-known/apple-app-site-association)
(https://你的域名/apple-app-site-association)
6.如果能够下载成功了，为了能够分享到微信和QQ，你还需要到微信开发者中心中和QQ互联中填写Universal Links并且需要验证
#7.在此强调一个重要的信息，第3步中的域名一旦填写，还有json文件一旦填写升级app既生效，如果想修改json中的信息，只能等app下次升级才能起作用(或者卸载app重装)（大坑，大坑）。一旦你的rul链接中有第3步中的域名，那么他们会微信和safari中直接调起app，所以，第3步中的域名要使用平时你们的分享以及业务不用到的域名。
相关文档
* The `apple-app-site-association` file is cached *once* when the app is first installed.
* If this initial scrape fails, in almost all situations it will not be reattempted. The only exception to this is if the initial return is a 5xx error, in which case a limited number of retries may occur. This is not well-documented, and is not covered in Universal Links documentation at all. You can find a mention in the [Shared Web Credentials docs](https://developer.apple.com/reference/security/1654440-shared_web_credentials).
* The file is *not* checked at all when a Universal Link is opened. This is why you are able to get Universal Links behavior in airplane mode.
* The file does not expire. Once it is cached, it sticks permanently for as long as the app is installed.
* The file will be re-checked when installing an app update.
* The file must be accessible via a valid SSL connection at either `https://example.com/apple-app-site-association` or `https://example.com/.well-known/apple-app-site-association`. If there are redirects of any kind, this will fail.
* It is theoretically possible to MITM the request if you are able to install a new SSL certificate directly on the device in question. [Charles Proxy](https://www.charlesproxy.com) for example uses this approach for debugging. I have never seen or heard of this being exploited, and the damage would be quite limited because the domain still has to be specified inside the app itself.
