blocks|key|366297|text|您可以使用以下代码进行迭代：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|366298|boost::property_tree::basic_ptree<std::string,std::string>::const_iterator+iter+=+pt.begin(),iterEnd+=+pt.end();
for(;iter+!=+iterEnd;%2B%2Biter)
{
+++++iter->first;+//+Your+key,+at+this+level+it+will+be+"electron",+"proton",+"proton"
+++++iter->second;+//+The+object+at+each+step+{"pos":+[0,0,0],+"vel":+[0,0,0]},+etc.
}|code-block|syntax|javascript|366299|希望能有所帮助|366300|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|K|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|L|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|M|8|@]|9|@]|A|$]]|$1|I|3|-4|5|6|7|N|8|@]|9|@]|A|$]]]|J|$]]

You can iterate with the following code :

<pre><code>boost::property_tree::basic_ptree&lt;std::string,std::string&gt;::const_iterator iter = pt.begin(),iterEnd = pt.end();
for(;iter != iterEnd;++iter)
{
 iter-&gt;first; // Your key, at this level it will be "electron", "proton", "proton"
 iter-&gt;second; // The object at each step {"pos": [0,0,0], "vel": [0,0,0]}, etc.
}
</code></pre>

Hope it helps

blocks|key|148081|text|我稍微修改了一下你的JSON。稍微未经测试的代码。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|148082|{
++++"particles":+[
++++++++{
++++++++++++"electron":+{
++++++++++++++++"pos":+[
++++++++++++++++++++0,
++++++++++++++++++++0,
++++++++++++++++++++0
++++++++++++++++],
++++++++++++++++"vel":+[
++++++++++++++++++++0,
++++++++++++++++++++0,
++++++++++++++++++++0
++++++++++++++++]
++++++++++++},
++++++++++++"proton":+{
++++++++++++++++"pos":+[
++++++++++++++++++++-1,
++++++++++++++++++++0,
++++++++++++++++++++0
++++++++++++++++],
++++++++++++++++"vel":+[
++++++++++++++++++++0,
++++++++++++++++++++-0.1,
++++++++++++++++++++-0.1
++++++++++++++++]
++++++++++++}
++++++++}
++++]
}|code-block|syntax|javascript|148083|..。|148084|#ifdef+_MSC_VER
#include+<boost/config/compiler/visualc.hpp>
#endif
#include+<boost/property_tree/ptree.hpp>
#include+<boost/property_tree/json_parser.hpp>
#include+<boost/foreach.hpp>
#include+<cassert>
#include+<exception>
#include+<iostream>
#include+<sstream>
#include+<string>

int+main()
{
++++try
++++{
++++++++std::stringstream+ss;
++++++++//+send+your+JSON+above+to+the+parser+below,+but+populate+ss+first


++++++++boost::property_tree::ptree+pt;
++++++++boost::property_tree::read_json(ss,+pt);

++++++++BOOST_FOREACH(boost::property_tree::ptree::value_type+&v,+pt.get_child("particles.electron"))
++++++++{
++++++++++++assert(v.first.empty());+//+array+elements+have+no+names
++++++++++++std::cout+<<+v.second.data()+<<+std::endl;
++++++++++++//+etc
++++++++}
++++++++return+EXIT_SUCCESS;
++++}
++++catch+(std::exception+const&+e)
++++{
++++++++std::cerr+<<+e.what()+<<+std::endl;
++++}
++++return+EXIT_FAILURE;
}|148085|按您认为合适的方式修改。|148086|打印整个树以查看正在读取的内容。这有助于调试。|148087|void+print(boost::property_tree::ptree+const&+pt)
{
++++using+boost::property_tree::ptree;
++++ptree::const_iterator+end+=+pt.end();
++++for+(ptree::const_iterator+it+=+pt.begin();+it+!=+end;+%2B%2Bit)+{
++++++++std::cout+<<+it->first+<<+":+"+<<+it->second.get_value<std::string>()+<<+std::endl;
++++++++print(it->second);
++++}
}|148088|entityMap^0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|U|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|W|8|@]|9|@]|A|$]]|$1|M|3|N|5|6|7|X|8|@]|9|@]|A|$]]|$1|O|3|P|5|D|7|Y|8|@]|9|@]|A|$E|F]]|$1|Q|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]]|R|$]]

I modified your JSON a bit. Slightly untested code.

<pre><code>{
 "particles": [
 {
 "electron": {
 "pos": [
 0,
 0,
 0
 ],
 "vel": [
 0,
 0,
 0
 ]
 },
 "proton": {
 "pos": [
 -1,
 0,
 0
 ],
 "vel": [
 0,
 -0.1,
 -0.1
 ]
 }
 }
 ]
}
</code></pre>

...

<pre><code>#ifdef _MSC_VER
#include &lt;boost/config/compiler/visualc.hpp&gt;
#endif
#include &lt;boost/property_tree/ptree.hpp&gt;
#include &lt;boost/property_tree/json_parser.hpp&gt;
#include &lt;boost/foreach.hpp&gt;
#include &lt;cassert&gt;
#include &lt;exception&gt;
#include &lt;iostream&gt;
#include &lt;sstream&gt;
#include &lt;string&gt;

int main()
{
 try
 {
 std::stringstream ss;
 // send your JSON above to the parser below, but populate ss first


 boost::property_tree::ptree pt;
 boost::property_tree::read_json(ss, pt);

 BOOST_FOREACH(boost::property_tree::ptree::value_type &amp;v, pt.get_child("particles.electron"))
 {
 assert(v.first.empty()); // array elements have no names
 std::cout &lt;&lt; v.second.data() &lt;&lt; std::endl;
 // etc
 }
 return EXIT_SUCCESS;
 }
 catch (std::exception const&amp; e)
 {
 std::cerr &lt;&lt; e.what() &lt;&lt; std::endl;
 }
 return EXIT_FAILURE;
}
</code></pre>

Modify as you see fit.

Print the entire tree to see what is being read. This helps in debugging.

<pre><code>void print(boost::property_tree::ptree const&amp; pt)
{
 using boost::property_tree::ptree;
 ptree::const_iterator end = pt.end();
 for (ptree::const_iterator it = pt.begin(); it != end; ++it) {
 std::cout &lt;&lt; it-&gt;first &lt;&lt; ": " &lt;&lt; it-&gt;second.get_value&lt;std::string&gt;() &lt;&lt; std::endl;
 print(it-&gt;second);
 }
}
</code></pre>

blocks|key|148123|text|我只是在更正上面答案的问题，但我无法在评论中获得正确的格式：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|148124|#ifdef+_MSC_VER
#include+<boost/config/compiler/visualc.hpp>
#endif
#include+<boost/property_tree/ptree.hpp>
#include+<boost/property_tree/json_parser.hpp>
#include+<boost/foreach.hpp>
#include+<cassert>
#include+<exception>
#include+<iostream>
#include+<sstream>
#include+<string>

void+print(boost::property_tree::ptree+const&+pt)
{
++++using+boost::property_tree::ptree;
++++ptree::const_iterator+end+=+pt.end();
++++for+(ptree::const_iterator+it+=+pt.begin();+it+!=+end;+%2B%2Bit)+{
++++++++std::cout+<<+it->first+<<+":+"+<<+it->second.get_value<std::string>()+<<+std::endl;
++++++++print(it->second);
++++}
}

int+main()
{
++++try
++++{
++++++++std::stringstream+ss;
++++++++//+send+your+JSON+above+to+the+parser+below,+but+populate+ss+first

++++++++ss+<<+"{+\"particles\":+[+{+\"electron\":+{+\"pos\":+[+0,+0,+0+],+\"vel\":+[+0,+0,+0+]+},+\"proton\":+{+\"pos\":+[+-1,+0,+0+],+\"vel\":+[+0,+-0.1,+-0.1+]+}+}+]}";


++++++++boost::property_tree::ptree+pt;
++++++++boost::property_tree::read_json(ss,+pt);

++++++++BOOST_FOREACH(boost::property_tree::ptree::value_type+&v,+pt.get_child("particles"))
++++++++{
++++++++++++assert(v.first.empty());+//+array+elements+have+no+names
++++++++++++print(v.second);
++++++++}
++++++++return+EXIT_SUCCESS;
++++}
++++catch+(std::exception+const&+e)
++++{
++++++++std::cerr+<<+e.what()+<<+std::endl;
++++}
++++return+EXIT_FAILURE;
}|code-block|syntax|javascript|148125|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

Just correcting issues with the answer above but I couldnt get the formating correct in the comments:

<pre><code>#ifdef _MSC_VER
#include &lt;boost/config/compiler/visualc.hpp&gt;
#endif
#include &lt;boost/property_tree/ptree.hpp&gt;
#include &lt;boost/property_tree/json_parser.hpp&gt;
#include &lt;boost/foreach.hpp&gt;
#include &lt;cassert&gt;
#include &lt;exception&gt;
#include &lt;iostream&gt;
#include &lt;sstream&gt;
#include &lt;string&gt;

void print(boost::property_tree::ptree const&amp; pt)
{
 using boost::property_tree::ptree;
 ptree::const_iterator end = pt.end();
 for (ptree::const_iterator it = pt.begin(); it != end; ++it) {
 std::cout &lt;&lt; it-&gt;first &lt;&lt; ": " &lt;&lt; it-&gt;second.get_value&lt;std::string&gt;() &lt;&lt; std::endl;
 print(it-&gt;second);
 }
}

int main()
{
 try
 {
 std::stringstream ss;
 // send your JSON above to the parser below, but populate ss first

 ss &lt;&lt; "{ \"particles\": [ { \"electron\": { \"pos\": [ 0, 0, 0 ], \"vel\": [ 0, 0, 0 ] }, \"proton\": { \"pos\": [ -1, 0, 0 ], \"vel\": [ 0, -0.1, -0.1 ] } } ]}";


 boost::property_tree::ptree pt;
 boost::property_tree::read_json(ss, pt);

 BOOST_FOREACH(boost::property_tree::ptree::value_type &amp;v, pt.get_child("particles"))
 {
 assert(v.first.empty()); // array elements have no names
 print(v.second);
 }
 return EXIT_SUCCESS;
 }
 catch (std::exception const&amp; e)
 {
 std::cerr &lt;&lt; e.what() &lt;&lt; std::endl;
 }
 return EXIT_FAILURE;
}
</code></pre>

I have a file like this:

[data.json]

<pre><code>{
 "electron": {
 "pos": [0,0,0],
 "vel": [0,0,0]
 },

 "proton": {
 "pos": [1,0,0],
 "vel": [0,0.1,0]
 },

 "proton": {
 "pos": [-1,0,0],
 "vel": [0,-0.1,-0.1]
 }
}
</code></pre>

How do I create a vector of particles from parsing this file. As I understand it I need to read the file using boost and read the strings (lines) into a vector, and then parse the contents of the vector.

The class particle is something like this:

<pre><code>class Particle
{

 private:
 particle_type mtype; // particle_type is an enum
 vector&lt;double&gt; mPos;
 vector&lt;double&gt; mVel;
};
</code></pre>

Other methods for get/set have been omitted in the class.

Basically I would like help creating a <code>vector&lt;Particle&gt;</code> with the correct position and velocity data and particle_type data parsed into it. Thanks in advance.

Code in main:

<pre><code>int main(){

 boost::property_tree::ptree pt;
 boost::property_tree::read_json("data.json", pt);
}
</code></pre>

Reading json file with boost

JSON

我有一个这样的文件：data.json{    "electron": {        "pos": [0,0,0],        "vel": [0,0,0]    },    "proton": {        "pos": [1,0,0],        "vel": [0,0.1,0]    },    ...

问使用boost读取json文件
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