How to use QFutureInterface?

[Michael_BJFU]

I want to use QFutureInterface, but its doc is not provided in Qt Assistant. So I have to use the Qt Creator source to have a look at how it is used.
The codes look like these:

static void find_helper(QFutureInterface<Usage> &future,
                        const CppModelManagerInterface::WorkingCopy workingCopy,
                        const LookupContext context,
                        CppFindReferences *findRefs,
                        Symbol *symbol){....}
const CppModelManagerInterface::WorkingCopy workingCopy = _modelManager->workingCopy();
    QFuture<Usage> result;
    result = QtConcurrent::run(&find_helper, workingCopy,
                               parameters.context, this, parameters.symbol);

static void find_helper(QFutureInterface<Usage> &future,
                        const CppModelManagerInterface::WorkingCopy workingCopy,
                        const LookupContext context,
                        CppFindReferences *findRefs,
                        Symbol *symbol){....}
const CppModelManagerInterface::WorkingCopy workingCopy = _modelManager->workingCopy();
    QFuture<Usage> result;
    result = QtConcurrent::run(&find_helper, workingCopy,
                               parameters.context, this, parameters.symbol);

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Note that the first parameter is not provided by the caller!!!Just like the pointer "this". Why ? When I write a code snippet like that, it complied error.
Can Anyone help me ? Thanks.