initialization with '{...}' expected for aggregate object

Question

I am trying to do string parsing (and it is proving to be a huge pain). I'm getting this error: "initialization with '{...}' expected for aggregate object "

I have an element defined like this:

Element * currentBar = new Element("Bar");

I want to make an array or something to store multiple bars, so I am trying to do something like this:

Element allBars [] = new Element("Bars");

I am pretty sure this is not what I want to do, especially since I am getting this error "initialization with '{...}' expected for aggregate object "

This is a segment of my code:

if(!chartDataString.empty()){ 
    chartData.clear();
    int index = 0;
    char c, c1, c2;
    inputMode currentInputMode = inputMode::UNKNOWN;
    Element * cur = NULL;
    while(index<chartDataString.size()){
        c = chartDataString[index];
        c1 = chartDataString[index+1];
        c2 = chartDataString[index+2];
        string s;
        s = c1;
        Element * currentBar = new Element("Bar");
        Element allBars [] = new Element("Bars");                               
            if(c == '*'){
            if(c1 == 'i'){
                currentBar->addChild(Element("rehearsalLetter", "info"));
            }
            else{
                currentBar->addChild(Element("leftDoubleBarLine", s));
                index++;
            }
        else if(c == '['){
            currentBar->addChild(Element("leftDoubleBarLine"));
        }
        else if(c == 'T'){
            string signature = string() + c1 + '/' + c2;
            currentBar->addChild(Element("timeSignature", signature));
            index += 2;
        }
        //start a new bar
        else if(c == '|'){
            allBars->addChild(currentBar);
            currentBar = new Element("bar");
        }

And my element class just in case it's helpful:

#include <string>
#include <ostream>
#include "ArrayList.h"


class Element{
public:
    Element(){}
    Element( const string& _title ){
        title = _title;
    }
    Element( const string& _title, const string& _value){
        title = _title;
        value = _value;
    };
    ~Element(){};

    void addChild(Element & child){
        children.add(child);
    }

    void serialize(ostream & o ){
        if( children.size() == 0 ){
            o << "<" << title << ">";
            o << " " << value << " ";
            o << "</" << title << ">";
        }else{
            o << "<" << title << ">" << endl;
            for( int i = 0; i < children.size(); ++i ){
                children.elementAt(i).serialize(o);
            }
            o << "</" << title << ">" << endl;
        }
    }
private:
    string title;
    string value;
    ArrayList<Element> children;

};

Solution

When you declare a variable Element allBars [] the compiler does expect a list of values like { Element("Bar"), Element("Foo") }. This is a static array whose size is known at compile time. So for example:

Element allBars [] = { Element("Bar"), Element("Foo") };

(Beware some compiler do require the number of element to be specified in the []).

If you want to declare a dynamic array, either you use a std::vector<Element> allBars;, which I would strongly recommend, because it cause grow and shrink without you worrying for memory allocation and deallocation. Your class should have a default constructor, a copy constructor and an assignment operator (even if generated by the compiler).

Or you use a pointer that you fill with new Element[xxx] like Element* allBars = new Element[size_of_array];, that cannot grow nor shrink and that you will have to explicitly delete using delete[] in order to call the Element destructor for every element of your array.

In both case, each Elementof the array will be initialized using the default constructor.

Comments

[Kerrek SB]

Try std::vector<Element>. Dynamic arrays are a wart and a cancer that doesn't fit into the language. There are multiple defect reports open concerning dynamic arrays.

[Sarah]

I have an array list class, it is possible just to make an array list of the bars?

[Lightness Races in Orbit]

(Beware some compiler do require the number of element to be specified in the []). For example? Such compilers would be non-conformant.

[Johan]

As I do not see the ArrayList code, I do not know :) But vector is great. Hard to beat in term of safety and performance for an array. The only problem is when you have a huge number of value that you can afford to store contiguously.

[Lightness Races in Orbit]

@Johan: That's when you switch to std::deque

[Sarah]

Will doing this allow me to call addChild on allBars?

[Johan]

@LightnessRacesinOrbit Yep, good advice ;) And for the compiler, I think it is just an old version of a compiler that rise an error in one previous question. Have to check what it was.

[Johan]

@Sarah for (auto& elem: allBars) { elem.addChild(the_child); } if that suits you