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POHow to construct a container of MyClass, where MyClass constructor can throw?
 

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  1. POHow to construct a container of MyClass, where MyClass constructor can throw?
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    <p>I have something like:</p> <pre><code>#include "MyImage.hpp" // MyImage wraps the Qt library image class namespace fs = boost::filesystem; class ImageCollection { public: ImageCollection(const char* path); private: const fs::path path_; deque&lt;MyImage&gt; instanceDeque_; } ImageCollection(const char* path) : path_(fs::is_directory(path) ? fs::complete(path) : fs::complete(path).parent_path()) /* Can I even do this? */ { /*** code in question ***/ fs::directory_iterator endIter; for(fs::directory_iterator dirIter(path_); dirIter != endIter; dirIter++) { instanceDeque_.push_back(MyImage(*dirIter)); } } </code></pre> <p>The MyImage constructor throws a MyInvalidFileException when *dirIter is a fs::path to a non-image file.</p> <p>I'd like MyImage and ImageCollection to be immutable.</p> <p>Can I:</p> <pre><code>try { instanceDeque_.push_back(MyImage(*dirIter)); } catch(const MyInvalidFileException&amp; e) { // oops, tnx Nemanja T. // remember *dirIter in a list of non-Image files, to use later continue; } </code></pre> <p>What happens when it throws? Is there a zombie MyImage or a zombie element left in the deque? Or is this actually the right way to do it? (i.e. the push_back() is aborted and no MyImage is created.)</p> <p>I currently have a messy workaround:</p> <pre><code>// load up an empty MyImage, which I'd rather not do instanceDeque_.push_back(MyImage()); for(fs::directory_iterator dirIter(path_); dirIter != endIter; dirIter++) { MyImage&amp; attemptImage = instanceDeque_.back(); bool success = attemptImage.loadPath(*dirIter); // "fill" the empty MyImage if (success) instanceDeque_.push_back(MyImage()); // prepare another empty MyImage } instanceDeque_.pop_back(); // discard the empty MyImage </code></pre> <p>Where MyImage is initialized with a null QImage*, and loadPath() creates a QImage on the heap. This forces me to have null pointer checks everywhere. I figure there should be a way to have an instance of QImage if the file can be opened, and the construction to just fail if the file can't.</p>
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    1. COCatch by const reference, not by value.
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      1. POHow to construct a container of MyClass, where MyClass constructor can throw?
      1. USNemanja Trifunovic
    2. COWhy are you using Boost to manage paths when QDir and friends are right there? Also deque is kind of useless, as QList performs very good in many cases and provides a cleaner and easier to use API.
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    3. COHow is the QList interface better? It looks exactly the same to me.
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