I think what you are looking for is a constructor for your new type that
uses incomplete initialization
type ExampleEvent
fld1::ASCIIString
fld2::Int16
fld3::Int64
fld4::Int64
fld5::Int64
fld6::Int64
fld7::Int64
function ExampleEvent(fld1, fld2)
obj = new() # create new object, without assigning values to
fields
obj.fld1 = fld1
obj.fld2 = fld2
return obj
end
end
Now you can use this constructor when assigning elements to the array
events = Vector{ExampleEvent}(1000)
for i=1:10
events[i] = ExampleEvent("abc", i)
end
events[5].fld3 = 7 # assign to previously undefined field
Note that you will get an error if you try to read a value from a field
that hasn't been set yet:
event = ExampleEvent("abc", 2)
y = event.fld3 # error, accessing undefined reference
Best,
Jared Crean
On Friday, July 22, 2016 at 2:38:27 PM UTC-4, [email protected] wrote:
>
>
> Thanks Cameron.
>
> What I wanted to do was assign values to fields but the example you posted
> requires me to pass values to all fields in my type.
>
> If I do: events[1] = ExampleEvent("asdf",123), julia throws an error since
> I need to pass values to ALL my type's fields. I don't always have to use
> all fields & sometimes do not have data for all fields, thus I don't want
> to be obligated to pass even null values to them since it is
> verbose/excessive. Nor do I want to rewrite constructors for all fields
> since I already have named fields for sake of programming ease.
>
> See what I mean?
>
> Moreover, let's say I've filled 10 elements of my 1000 element array & a
> few milliseconds later I get a value for element 5, fld3. How do I index
> into element 5 of the events Vector & ONLY set fld3?
>
> Yes I've seen push! & looks good but I'm pretty religious about
> precallocating in any lang even if it is much larger than needed since
> processing these datasets require as much efficiency as possible.
>
> I think more intuitive Composite Type Arrays for morons like me would make
> Juila much easier to work with since I've seen a fair amount of
> uncertainty/confusion from people having similar conceptual use cases. I
> know I'm thinking from a perspective of other language(s) but some language
> constructs are there because they work & make a programmer's life easier.
> Is there an easy way to set field value(s) whenever I get them?
>
> On Friday, July 22, 2016 at 2:01:41 PM UTC-4, Cameron McBride wrote:
>>
>> Your ExampleEvent is completely analagous to a C-like struct. With
>> Stefan's bit, you now have a single dimension array of ExampleEvent type
>> (hence ndims(events) is 1).
>>
>> You can do this:
>> julia> events[1] = ExampleEvent("asdf",2,3,4,5,6,7)
>> ExampleEvent("asdf",2,3,4,5,6,7)
>>
>> And if you have more, you can do this:
>> julia> push!(events, ExampleEvent("ghjk", 2,3,4,5,6,7))
>> 1001-element Array{ExampleEvent,1}:
>> ExampleEvent("asdf",2,3,4,5,6,7)
>> #undef
>> ⋮
>> #undef
>> ExampleEvent("ghjk",2,3,4,5,6,7)
>>
>> Cameron
>>
>> On Fri, Jul 22, 2016 at 1:48 PM, <[email protected]> wrote:
>>
>>> Thanks Stefan!
>>>
>>> I thought it would be like declaring a struct array in c/c++ i.e.
>>> something like ExampleEvent events[2][1000]; Then set each field in the
>>> events array as I encounter the required value in my algo: e.g.
>>> events[1][1].fld1 = "ABC"; events[1][1].fld2 = 123; etc
>>>
>>> How do I access elements in the events Vector since ndims(events) = 1? I
>>> don't see anything in the docs about indexing into a preallocated Vector
>>> data structure. I see methods like push! splice! etc but not anything that
>>> will let me use the elements of my preallocation on the fly.
>>>
>>>
>>> On Thursday, July 21, 2016 at 3:21:54 PM UTC-4, Stefan Karpinski wrote:
>>>>
>>>> It's a little unclear what you want to do that you can't figure out how
>>>> to accomplish. You can allocate an uninitialized vector of ExampleEvent
>>>> objects:
>>>>
>>>> julia> type ExampleEvent
>>>> fld1::ASCIIString
>>>> fld2::Int16
>>>> fld3::Int64
>>>> fld4::Int64
>>>> fld5::Int64
>>>> fld6::Int64
>>>> fld7::Int64
>>>> end
>>>>
>>>> julia> events = Vector{ExampleEvent}(1000)
>>>> 1000-element Array{ExampleEvent,1}:
>>>> #undef
>>>> #undef
>>>> #undef
>>>> ⋮
>>>> #undef
>>>> #undef
>>>> #undef
>>>>
>>>>
>>>>
>>>>
>>>> On Thu, Jul 21, 2016 at 2:51 PM, <[email protected]> wrote:
>>>>
>>>>>
>>>>> Hi
>>>>>
>>>>> I was working on processing large data sets & historically I've used
>>>>> structs in C++ & other languages for this type of task. I attempted to
>>>>> use
>>>>> a Composite Type in Julia & preallocate a large array before filling it
>>>>> w/values as my algo processes the data.
>>>>>
>>>>> My example was:
>>>>>
>>>>> type ExampleEvent
>>>>>
>>>>> fld1::ASCIIString
>>>>> fld2::Int16
>>>>> fld3::Int64
>>>>> fld4::Int64
>>>>> fld5::Int64
>>>>> fld6::Int64
>>>>> fld7::Int64
>>>>>
>>>>> end
>>>>>
>>>>> I googled around & from what I found, & all the docs examples I tried
>>>>> out, there isn't an obvious way to declare an array of composite type
>>>>> without having to do some work arounds.
>>>>>
>>>>> I liked the language in several other respects but it seems to be
>>>>> missing helpful tools to make the programmer's life easy. Am I missing
>>>>> something? If not, why is a data structure like this not easily
>>>>> available?
>>>>>
>>>>> thanks in advance
>>>>>
>>>>> best,
>>>>> A
>>>>>
>>>>
>>>>
>>
