'RXJava persist return value of previous flatMap

In RX JAVA(java8), how can I persist value of previous flatMap or map.

public void createAccount(]) {
    JsonObject payload = routingContext.getBodyAsJson();
    socialService.getOAuthToken(payload)
            .flatMap(token -> {
                return getAllAccounts(token);
            })
            .flatMap(accounts -> {
                // Save accounts with TOKENS
            })
            .subscribe(accountID -> {
                  response(accountID);
            );
}

So in above code, in second flatMap how can I get the token from previous flatMap.

javarx-java


Solution 1:[1]

You have to zip account and token and pass it to the next Stream operation.

//Note you have to replace T, A with the right type
socialService.getOAuthToken(payload).flatMap(token -> getAllAccounts(token)
        .map(account -> new SimpleImmutableEntry<T, A>(token, account)))
     .flatMap(accounts -> /* accounts.getKey() -> token, accounts.getValue() -> account */)
     .subscribe(accountId -> response(accountId));

Solution 2:[2]

Kotlin solution based on the solution by @Flown:

socialService.getOAuthToken(payload)
    .flatMap { token -> 
        getAllAccounts(token)
            .map { account -> Pair(token, account) }
     }
     .flatMap { (token, account) -> /* Use values here */ }
     .subscribe { accountId -> response(accountId) }

Sources

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Source: Stack Overflow

Solution Source
Solution 1 Flown
Solution 2 molundb

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