Listmodel and large amount of data
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@huot: those 30 items:
- Are they structured or indexed or something like that, or is it one huge list?
- Is your data random accessible or not?
- Are these items big (kilobytes) or small (a few bytes each)?
- Are all your items going to be same size, or do they have different sizes?
- ...
You are simply not providing enough information.
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Maybe I didn't make myself clear enough.
I am developing a bible reader application for Nokia N9. As you may know the bible consists of books, chapters and verses. Item of the model is similar to bible verse. The data added to the model one chapter at a time (consist of many verses). If the user picks a verse he should be able to scroll both backwards and forwards.
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Please, practice a bit of patience. Kicking your issue this fast is not considdered very polite, we both have day jobs and families that demand our attention as well.
It seems to me your data is very easy to structure. Do you want to have all books, chapters and verses in one big list? Or do you think structuring the data is acceptable?
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I'm sorry if I seemed too impatient. I didn't mean to be rude. I was thinking that all books, chapters and verses would be in one big list so that it is easy for the user to scroll the book back and forth. I don't know if this is a good idea but this is how I have thought it.
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huot,
I've started to port symbianbible (http://compactbyte.com/symbianbible/) to qt (https://groups.google.com/forum/?fromgroups#!topic/symbianbible/lbSRh8e0r_o).
The PalmVersion of Bible Reader (Bible++) had same problem: performance.
Yohanes (the author) keep the original reader code, bacause is optimzed (low memory, low speed).
I'm starting to port (not recompiliing) the PDB reader and mantain the same structures, because there's a lot PDB bible files in the net. But I'm thinking to migrate the data to SqlLite.
I'd have pushed the initial source code (initial focus to PDB Reader ) to bitbucket, but I'll migrate to github.
Can you check the sources?
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I'd forgot the link to the project at BitBucket:
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TioRay:
I use Sword project (www.crosswire.org/sword) as backend.Volker:
I tried to implement your suggestion of "lazy loading" but I didn't get it working. The problem is that in the data() method the data of the model can't be modified because data() method is CONST.Any suggestions how to solve this problem?
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Just mark the storage member of your model subclass as mutable. This way you can modify it even in a const method.
Doing so is perfectly ok in your case, as the const of data() promises to not change the logical state of your object. In case of lazy loading, you do not change the logical state, but only the physical representation (i.e. the bits and bytes).
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[quote author="Volker" date="1332158256"]Just mark the storage member of your model subclass as mutable. This way you can modify it even in a const method.
Doing so is perfectly ok in your case, as the const of data() promises to not change the logical state of your object. In case of lazy loading, you do not change the logical state, but only the physical representation (i.e. the bits and bytes).[/quote]
Volker:
I tried your suggestion. The problem is that I can't call beginInsertRows() function within data() function because beginInsertRows() function isn't CONST.
It seems to be very difficult to implement this with Qt. Any new suggestions are welcome!