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I am using Oraclize for randomness. The range of random numbers I want depends on a variable maxNumber, and will be 0 - maxNumber.

If you scroll to the right of my code snippet below, you'll see maxNumber which I intuitively attempted to concat using +.

Off course that doesn't work and I get a compiler error since I cannot concat uint to a bytes32.

What is the proper way to concat in this situation?

bytes32 queryId = oraclize_query(
            "nested", 
            "[URL] ['json(https://api.random.org/json-rpc/1/invoke).result.random[\"data\"]', '\\n{\"jsonrpc\": \"2.0\", \"method\": \"generateIntegers\", \"params\": { \"apiKey\": \"keyGoesHere\"}\", \"n\": 1,\"min\": 0, \"max\":'"+maxNumber-1+"', \"replacement\": true }, \"id\": 14215${[identity] \"}\"}']",
            gasForOraclize
        );
Ryan Miller
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1 Answers1

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Use the uint2string method to convert the variable which holds a number (maxNumber) to a string. If you want to make the max range = maxNumber - 1 decrement maxNumber before the oraclize query as shown below.

uint maxNumber -= 1;

oraclize_query(
        "nested", 
        "[URL] ['json(https://api.random.org/json-rpc/1/invoke).result.random[\"data\"]', '\\n{\"jsonrpc\": \"2.0\", \"method\": \"generateIntegers\", \"params\": { \"apiKey\": \"keyGoesHere\"}\", \"n\": 1,\"min\": 0, \"max\": uint2str(maxNumber), \"replacement\": true }, \"id\": 14215${[identity] \"}\"}']",
        gasForOraclize
    );
savard
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  • Thanks. However, that does not work. In your example, the variable name is inside of a string literal. ... I would need to concatenate the value of that variable some how, no? – Ryan Miller Apr 28 '18 at 19:07
  • Oh ok, I believe this answer may help you then

    https://ethereum.stackexchange.com/a/28671/33496 , in that example they use strConcat, and make the oraclize query 3 different strings which they then concatenate

     – savard Apr 28 '18 at 22:24