JSON Object/Buffer parser issue

JsonObject& getECData(JsonBuffer& b, byte ecRangeIndex = 1){
    tmpFile = SD.open("dromatic/" + cropName + "/Crop/EC/ECRng" + ecRangeIndex + ".dro", O_READ);
    JsonObject& d = b.parseObject(tmpFile.readString());
    tmpFile.close();
    return d;
}

In the example I can't figure out how to "parseObject" to work with the JsonBuffer inside the JsonObject.

The error is that parseObject does not exist in JsonBuffer and I know this but being inside a JsonObject I though it would work I guess I don't understand why. Can any Help thanks in advanced

tmpFile.readString()

I don't see a readString method in the SD File class.

Maybe the example helps.

Find the documentation on the particular JSON library that you are using.