String and Array

General JUCE discussion
1

Hey guys,

I’m getting access violations. In particular:

class StringCopyTest
{
public:
	juce::String variable;
};

// 1 > ok
{
	StringCopyTest s1, s2;
	s1.variable = "Hello World";
	s2 = s1;
}

// 2 > ok
{
	std::vector<StringCopyTest> v1, v2;
	StringCopyTest s;
	s.variable = "Hello World";
	v1.push_back(s);
	v2 = v1;
}

// 3 > fails
{
	juce::Array<juce::String> a1, a2; 
	a1.add(T("Helo World"));
	a2 = a1;
}

// 4 > fails
{
	juce::Array<StringCopyTest> a1, a2;
	StringCopyTest s;
	s.variable = "Hello World";
	a1.add(s);
	a2 = a1;
}

Specifically any class that has String and is contained in Array will give an exception on copying the array.

Is this a bug? Am I missing something? Help! :slight_smile: I know there’s the StringArray which solves case 3, but case 4 isn’t helped by StringArray…

  • Bram
2

Array is only for simple types like int, char, bool, (MyClass *). For complex types that should be deleted with the array, use OwnedArray. For Strings use StringArray. Best is to read the JUCE docs for all this.

3

I’m curious and don’t understand the exact mechanics of this. I think I heard it’s because it uses malloc for the sizeof(…) the datatype, but I’m not sure why this excludes “complex types”. What makes a type complex?

4

Well think about it:

Is allocating space with malloc() for a class the same as using new operator for a class? … it isn’t. So Array will only work with simple types or structs (ok, complex types was not a good word choice from my side, let’s correct it to classes).

5

malloc won’t call the constructor, so no variables will be initialized. If it’s a class with virtual functions, the vtable won’t be setup either.

6

What a head-smacking moment. Of course malloc wouldn’t call a constructor. Well at least I’ll never forget, now… :shock:
Thanks, both.