How to iterate though each character of a string from a json file with Boost?

[wh1t3crayon]

I'm trying to load up a game level using a pseudomap that I have stored in a json file, but I don't know the syntax on how to iterate through every character of the string. Here is an example of the json pseudomap:

{
  levels{
    level1{
      "map": "wwwww...................\nww...................www",
    }
  }
}

So everywhere there is a 'w' I want to place a wall. The \n is a placeholder for a line break ina standard .txt file

Here is my attempt at this, but it doesn't compile

boost::property_tree::ptree pt;
boost::property_tree::read_json("levels/level" + std::to_string(levelNumber) + ".json", pt);
std::string pseudomap("levels.level1.map");
for(unsigned int i = 0; i < pt.get_child(pseudomap).size(); i++){
	if(pt.get_child(pseudomap)[i] == "w"){ //I want to treat pt like a vector of chars that I can iterate through
		AddWall();
	}
}

What doesn't compile is if(pt.get_child(pseudomap)[i] because I don't know how to access a specific element of the current string in a boost property tree. Can anybody help me solve this?

[Zhuge]

I used property_tree before and I don't have my code with me, but maybe this will help:

Do you really mean to use get_child() on map? It is just a string, so I would have thought that something like
pt.get<std::string>("levels.level1.map")
would get you a string that you can then do what you like with.

[wh1t3crayon]

Hmm okay, what about accessing elements in an array in a .json file?

{
	"levels":
	{
		"level1": {
			"map": "wwwww...................\nww...................www",
			"spawnpoints": [
				{"x": 20, "y": 30}
			],
			"itemSpawns": [
				{"itemType": "powerUp", "x": 100, "y": 30}
			]
		}
	}
}

How do I access "spawnpoints.x"?
pt.get<float>("levels.level1.spawnpoints.x" does not work

[MikeyBoy]

I'm no expert in boost property trees, but you've made "spawnpoints" an array (because of the square brackets [...]) containing a single element. So you'd need to specifically access the first element of that array.

Or, presumably, you really want to iterate over each element of that array in turn, if you're generalizing to more than one spawn point.

[Zhuge]

Guessing again, but maybe something like:

for(boost::property_tree::ptree::value_type &v : pt.get_child("levels.level1.spawnpoints")) {
    // use v, which IIRC is another property tree representing the subtree
    // in your case that would be a tree with x and y children, I think
}

[wh1t3crayon]

for(boost::property_tree::ptree::value_type &v : pt.get_child("levels.level1.spawnpoints"))

This for loop doesn't iterate at all. The code skips right over it

for(boost::property_tree::ptree::value_type &v : pt.get_child("levels.level1"))
However this foor loop does iterate

Okay so that code does work. In order to pause the program to check, I was placing a breakpoint on int i; when I needed to type int i = 0;

Here is the full loop

for(boost::property_tree::ptree::value_type &v : pt.get_child("levels.level1.spawnpoints")){
			spawnPoint.x = v.second.get<float>("x");
		}

Thanks guys