Destination not a pointer

[Josh Kamau]

Why does this tell me destination is not a pointer?

values := make([]interface{}, len(columns))
err := rows.Scan(values...)

Thanks

Josh

[DV]

The same reason this needs pointers:

http://play.golang.org/p/KL6iWq5Sb_

Go is pass by value. Passing in an argument creates a *copy* of that argument. So you end up modifying the copy, not the original. You're passing *copies* of your slice contents. "Scan" is being nice and letting you know you're doing something wrong, by examining what you passed in using reflection. 

[Josh Kamau]

HI DV ;

The challenge i have is  i am dealing with []interface {} ,  i tried passing &values but it didnt work. I even trying constructing the array in a loop using append(values, &valueInterface) so that i endup with []*value where a value is interface{} but it didnt work either.

Thanks
Josh

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[Josh Kamau]

This sort of  worked.

       var values = make([]interface{}, len(columns))
        for i, _ := range columns {
            values[i] = new(interface{})
        }
        err := rows.Scan(values...)

[Dave Cheney]

That doesn't make sense, you are asking rows.Scan to unpack each value into an interface{}, not a discrete type. Why don't you know the type of the columns you have requested ?

[Josh Kamau]

I was creating a generic function.  I ended up using gorp which does what i was trying to do. 

Thanks.

Josh

--

[Dave Cheney]

Right, thanks for confirming, in that case what you have done is not
the same as gorp

// gorp
s := make([]interface{}. 3)
s[0] = new(int)
s[1] = new(bool)
s[2] = new(string)

so rows.Scan(s...) will be able to interogate the types inside s

filling s with new(interface{}) won't give rows.Scan the information
it needs to unpack the data from the sql driver.