Allow dynamic URL

CHANGELOG.md

@@ -1,5 +1,8 @@
 # Changelog
 
+## v0.9.19 (TDB)
+- Allow for dynamic url [#847](https://github.com/apollographql/subscriptions-transport-ws/pull/847)
+
 ## v0.9.18 (2020-08-17)
 
 ### Bug Fixes

README.md

@@ -238,7 +238,7 @@ ReactDOM.render(
 
 ## SubscriptionClient
 ### `Constructor(url, options, webSocketImpl)`
-- `url: string` : url that the client will connect to, starts with `ws://` or `wss://`
+- `url: string | (() => string)` : url that the client will connect to, starts with `ws://` or `wss://` - can alternatively be a function that returns the connection url, which will be invoked every time the client tries to connect
 - `options?: Object` : optional, object to modify default client behavior
   * `timeout?: number` : how long the client should wait in ms for a keep-alive message from the server (default 30000 ms), this parameter is ignored if the server does not send keep-alive messages. This will also be used to calculate the max connection time per connect/reconnect
   * `minTimeout?: number`: the minimum amount of time the client should wait for a connection to be made (default 1000 ms)

src/client.ts

@@ -73,7 +73,7 @@ export interface ClientOptions {
 export class SubscriptionClient {
   public client: any;
   public operations: Operations;
-  private url: string;
+  private url: string | (() => string);
   private nextOperationId: number;
   private connectionParams: Function;
   private minWsTimeout: number;
@@ -100,7 +100,7 @@ export class SubscriptionClient {
   private wsOptionArguments: any[];
 
   constructor(
-    url: string,
+    url: string | (() => string),
     options?: ClientOptions,
     webSocketImpl?: any,
     webSocketProtocols?: string | string[],
@@ -554,7 +554,8 @@ export class SubscriptionClient {
   }
 
   private connect() {
-    this.client = new this.wsImpl(this.url, this.wsProtocols, ...this.wsOptionArguments);
+    const url = typeof this.url === 'string' ? this.url : this.url();
+    this.client = new this.wsImpl(url, this.wsProtocols, ...this.wsOptionArguments);
 
     this.checkMaxConnectTimeout();