C++ 遍历 JsonCpp 中的对象
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Iterating through objects in JsonCpp
提问by Steven smethurst
I have a C++ application that uses jsoncppto decode a JSON string. I have created the following function but it only shows me the top level objects...
我有一个 C++ 应用程序，它使用jsoncpp来解码 JSON 字符串。我创建了以下函数，但它只显示了顶级对象...
How do I get it to dump the entire object list?
我如何让它转储整个对象列表？
--Function--
- 功能 -
SaveJSON( json_data );
bool CDriverConfigurator::PrintJSONTree( Json::Value & root, unsigned short depth /* = 0 */)
{
printf( " {type=[%d], size=%d} ", root.type(), root.size() );
if( root.size() > 0 ) {
for( Json::ValueIterator itr = root.begin() ; itr != root.end() ; itr++ ) {
PrintJSONTree( itr.key(), depth+1 );
}
return true;
}
// Print depth.
for( int tab = 0 ; tab < depth; tab++) {
printf( "-");
}
if( root.isString() ) {
printf( " %s", root.asString().c_str() );
} else if( root.isBool() ) {
printf( " %d", root.asBool() );
} else if( root.isInt() ) {
printf( " %d", root.asInt() );
} else if( root.isUInt() ) {
printf( " %d", root.asUInt() );
} else if( root.isDouble() ) {
printf( " %f", root.asDouble() );
}
else
{
printf( " unknown type=[%d]", root.type() );
}
printf( "\n" );
return true;
}
--- Input ----
- - 输入 - -
{
"modules":[
{
"config":{
"position":[
129,
235
]
},
"name":"Modbus Task",
"value":{
"DeviceID":"This is the name",
"Function":"01_READ_COIL_STATUS",
"Length":"99",
"Scan":"111",
"Type":"Serve"
}
},
{
"config":{
"position":[
13,
17
]
},
"name":"Modbus Connection",
"value":{
"Baud":"9600",
"timeout":"2.5"
}
},
{
"config":{
"position":[
47,
145
]
},
"name":"Modbus Device",
"value":{
"DeviceID":"55"
}
},
{
"config":{
"position":[
363,
512
]
},
"name":"Function Something",
"value":{
}
},
{
"config":{
"position":[
404,
701
]
},
"name":"Function Something",
"value":{
}
}
],
"properties":{
"Blarrg":"",
"description":"",
"name":"Modbus"
},
"wires":[
{
"src":{
"moduleId":1,
"terminal":"modbus.connection.output"
},
"tgt":{
"moduleId":2,
"terminal":"modbus.connection.input"
}
},
{
"src":{
"moduleId":2,
"terminal":"modbus.device.output"
},
"tgt":{
"moduleId":0,
"terminal":"modbus.device.output"
}
},
{
"src":{
"moduleId":3,
"terminal":"dataOut"
},
"tgt":{
"moduleId":4,
"terminal":"dataIn"
}
},
{
"src":{
"moduleId":3,
"terminal":"dataIn"
},
"tgt":{
"moduleId":0,
"terminal":"data1"
}
}
]
}
--Output--
- 输出 -
{type=[7], size=3} {type=[4], size=0} - modules
{type=[4], size=0} - properties
{type=[4], size=0} - wires
回答by Omnifarious
You have some errors related to seemingly not having a great handle on recursion or the key->value nature of JSON and how that relates to the library you're using. I haven't tested this code at all, but it should work better.
您有一些与似乎没有很好地处理递归或 JSON 的键 > 值性质以及它与您使用的库的关系相关的错误。我根本没有测试过这段代码，但它应该工作得更好。
void CDriverConfigurator::PrintJSONValue( const Json::Value &val )
{
if( val.isString() ) {
printf( "string(%s)", val.asString().c_str() );
} else if( val.isBool() ) {
printf( "bool(%d)", val.asBool() );
} else if( val.isInt() ) {
printf( "int(%d)", val.asInt() );
} else if( val.isUInt() ) {
printf( "uint(%u)", val.asUInt() );
} else if( val.isDouble() ) {
printf( "double(%f)", val.asDouble() );
}
else
{
printf( "unknown type=[%d]", val.type() );
}
}
bool CDriverConfigurator::PrintJSONTree( const Json::Value &root, unsigned short depth /* = 0 */)
{
depth += 1;
printf( " {type=[%d], size=%d}", root.type(), root.size() );
if( root.size() > 0 ) {
printf("\n");
for( Json::Value::const_iterator itr = root.begin() ; itr != root.end() ; itr++ ) {
// Print depth.
for( int tab = 0 ; tab < depth; tab++) {
printf("-");
}
printf(" subvalue(");
PrintJSONValue(itr.key());
printf(") -");
PrintJSONTree( *itr, depth);
}
return true;
} else {
printf(" ");
PrintJSONValue(root);
printf( "\n" );
}
return true;
}
回答by JaredC
If you are just looking to print out the Json::Value, there's a methodfor that:
如果您只是想打印出 Json::Value，则有一种方法：
Json::Value val;
/*...build the value...*/
cout << val.toStyledString() << endl;
Also, you may want to look into the Json::StyledWriter, the documentation for it is here. I believe it print a human friendly version. Also, Json::FastWriter, documentation here, prints a more compact form.
此外，您可能想查看Json::StyledWriter它的文档在这里。我相信它会打印一个人性化的版本。此外，此处的Json::FastWriter文档打印出更紧凑的表格。
回答by BattleTested
This is a good example that can print either jsonobjects and object member (and it's value) :
这是一个很好的例子，可以打印json对象和对象成员（及其值）：
Json::Value root; // Json root
Json::Reader parser; // Json parser
// Json content
string strCarPrices ="{ \"Car Prices\": [{\"Aventador\":\"3,695\", \"BMW\":\",250\",\"Porsche\":\",000\",\"Koenigsegg Agera\":\".1 Million\"}]}";
// Parse the json
bool bIsParsed = parser.parse( strCarPrices, root );
if (bIsParsed == true)
{
// Get the values
const Json::Value values = root["Car Prices"];
// Print the objects
for ( int i = 0; i < values.size(); i++ )
{
// Print the values
cout << values[i] << endl;
// Print the member names and values individually of an object
for(int j = 0; j < values[i].getMemberNames().size(); j++)
{
// Member name and value
cout << values[i].getMemberNames()[j] << ": " << values[i][values[i].getMemberNames()[j]].asString() << endl;
}
}
}
else
{
cout << "Cannot parse the json content!" << endl;
}
The output :
输出 ：
{
"Aventador" : "3,695",
"BMW" : ",250",
"Koenigsegg Agera" : ".1 Million",
"Porsche" : ",000"
}
Aventador: 3,695
BMW: ,250
Koenigsegg Agera: .1 Million
Porsche: ,000
回答by Sergey Merkelov
There is an easy way to iterate over all fields in json::value. I omitted the printf stuff.
有一种简单的方法可以遍历 json::value 中的所有字段。我省略了 printf 的东西。
#include "cpprest/json.h"
#include "cpprest/filestream.h"
using web::json::value;
using std::wstring;
static void printOneValue(const wstring &key, const double &value);
static void printOneValue(const wstring &key, const bool &value);
static void printOneValue(const wstring &key, const int &value);
static void printOneValue(const wstring &key, const wstring &value);
static void printOne(const wstring &key, const value &v, _num level);
static void printTree(const value &v);
static void printTree(const value &v)
{
if(!v.is_object())
return;
try
{
printOne(wstring(), v, 0);
}
catch(...)
{
// error handling
}
}
static void printOne(const wstring &key, const value &v, _num level)
{
switch(v.type())
{
case value::value_type::Number:
if(v.is_double())
printOneValue(key, v.as_double());
else
printOneValue(key, v.as_integer());
break;
case value::value_type::Boolean:
printOneValue(key, v.as_bool());
break;
case value::value_type::String:
printOneValue(key, v.as_string());
break;
case value::value_type::Object:
for(auto iter : v.as_object())
{
const wstring &k = iter.first;
const value &val = iter.second;
printOne(k, val, level+1);
}
break;
case value::value_type::Array:
for(auto it : v.as_array())
{
printOne(key, it, level+1);
}
break;
case value::value_type::Null:
default:
break;
}
}
static void printOneValue(const wstring &key, const wstring &value)
{
// process your key and value
}
static void printOneValue(const wstring &key, const int &value)
{
// process your key and value
}
static void printOneValue(const wstring &key, const double &value)
{
// process your key and value
}
static void printOneValue(const wstring &key, const bool &value)
{
// process your key and value
}
