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|
### jsoncons::csv::encode_csv
Encodes a C++ data structure into the CSV data format.
```cpp
#include <jsoncons_ext/csv/csv.hpp>
template <typename T,typename CharContainer>
void encode_csv(const T& val, CharContainer& cont,
const basic_csv_encode_options<CharContainer::value_type>& options
= basic_csv_encode_options<CharContainer::value_type>()); (1)
template <typename T,typename CharT>
void encode_csv(const T& val, std::basic_ostream<CharT>& os,
const basic_csv_encode_options<CharT>& options
= basic_csv_encode_options<CharT>()); (2)
template <typename T,typename CharContainer>
void encode_csv(const allocator_set<Allocator,TempAllocator>& alloc_set,
const T& val, CharContainer& cont,
const basic_csv_encode_options<CharContainer::value_type>& options
= basic_csv_encode_options<CharContainer::value_type>()); (3) (since 0.171.0)
template <typename T,typename CharT>
void encode_csv(const allocator_set<Allocator,TempAllocator>& alloc_set,
const T& val, std::basic_ostream<CharT>& os,
const basic_csv_encode_options<CharT>& options
= basic_csv_encode_options<CharT>()); (4) (since 0.171.0)
```
(1) Writes a value of type T into a character container in the CSV data format, using the specified (or defaulted) [options](basic_csv_options.md).
Type 'T' must be an instantiation of [basic_json](../basic_json.md)
or support [json_type_traits](../json_type_traits.md).
(2) Writes a value of type T into an output stream in the CSV data format, using the specified (or defaulted) [options](basic_csv_options.md).
Type 'T' must be an instantiation of [basic_json](../basic_json.md)
or support [json_type_traits](../json_type_traits.md).
Functions (3)-(4) are identical to (1)-(2) except an [allocator_set](../allocator_set.md) is passed as an additional argument.
### Examples
[Encode a JSON array of "flat" objects (n_objects format)](#eg1)
[Encode a JSON array of "flat" arrays (n_rows format)](#eg2)
[Encode a JSON object of name-array members (m_columns format)](#eg3)
[Encode a JSON array of objects to CSV with subfields](#eg4)
[Encode nested JSON to CSV (since 1.2.0)](#eg5)
[Encode nested JSON to CSV with column mapping (since 1.2.0)](#eg6)
<div id="eg1"/>
```cpp
#include <cassert>
#include <iostream>
#include <jsoncons/json.hpp>
#include <jsoncons_ext/csv/csv.hpp>
namespace csv = jsoncons::csv;
int main()
{
const std::string jtext = R"(
[
{
"customer_name": "John Roe",
"has_coupon": true,
"phone_number": "0272561313",
"zip_code": "01001",
"sales_tax_rate": 0.05,
"total_amount": 431.65
},
{
"customer_name": "Jane Doe",
"has_coupon": false,
"phone_number": "416-272-2561",
"zip_code": "55416",
"sales_tax_rate": 0.15,
"total_amount": 480.7
},
{
"customer_name": "Joe Bloggs",
"has_coupon": false,
"phone_number": "4162722561",
"zip_code": "55416",
"sales_tax_rate": 0.15,
"total_amount": 300.7
},
{
"customer_name": "John Smith",
"has_coupon": false,
"phone_number": null,
"zip_code": "22313-1450",
"sales_tax_rate": 0.15,
"total_amount": 300.7
}
]
)";
auto j = jsoncons::ojson::parse(jtext);
std::string output;
auto ioptions = csv::csv_options{}
.quote_style(csv::quote_style_kind::nonnumeric);
csv::encode_csv(j, output, ioptions);
std::cout << output << "\n\n";
auto ooptions = csv::csv_options{}
.assume_header(true);
auto other = csv::decode_csv<jsoncons::ojson>(output, ooptions);
assert(other == j);
}
```
Output:
```
customer_name,has_coupon,phone_number,zip_code,sales_tax_rate,total_amount
"John Roe",true,"0272561313","01001",0.05,431.65
"Jane Doe",false,"416-272-2561","55416",0.15,480.7
"Joe Bloggs",false,"4162722561","55416",0.15,300.7
"John Smith",false,null,"22313-1450",0.15,300.7
```
<div id="eg2"/>
#### Encode a json array of arrays (n_rows format)
```cpp
#include <cassert>
#include <iostream>
#include <jsoncons/json.hpp>
#include <jsoncons_ext/csv/csv.hpp>
namespace csv = jsoncons::csv;
int main()
{
const std::string jtext = R"(
[
["customer_name","has_coupon","phone_number","zip_code","sales_tax_rate","total_amount"],
["John Roe",true,"0272561313","01001",0.05,431.65],
["Jane Doe",false,"416-272-2561","55416",0.15,480.7],
["Joe Bloggs",false,"4162722561","55416",0.15,300.7],
["John Smith",false,null,"22313-1450",0.15,300.7]
]
)";
auto j = jsoncons::json::parse(jtext);
std::string output;
auto ioptions = csv::csv_options{}
.quote_style(csv::quote_style_kind::nonnumeric);
csv::encode_csv(j, output, ioptions);
std::cout << output << "\n\n";
auto ooptions = csv::csv_options{}
.assume_header(true)
.mapping_kind(csv::csv_mapping_kind::n_rows);
auto other = csv::decode_csv<jsoncons::json>(output, ooptions);
assert(other == j);
}
```
Output:
```
"customer_name","has_coupon","phone_number","zip_code","sales_tax_rate","total_amount"
"John Roe",true,"0272561313","01001",0.05,431.65
"Jane Doe",false,"416-272-2561","55416",0.15,480.7
"Joe Bloggs",false,"4162722561","55416",0.15,300.7
"John Smith",false,null,"22313-1450",0.15,300.7
```
<div id="eg3"/>
#### Encode a json object of name-array members (m_columns format)
```cpp
#include <cassert>
#include <iostream>
#include <jsoncons/json.hpp>
#include <jsoncons_ext/csv/csv.hpp>
namespace csv = jsoncons::csv;
int main()
{
const std::string jtext = R"(
{
"customer_name": ["John Roe","Jane Doe","Joe Bloggs","John Smith"],
"has_coupon": [true,false,false,false],
"phone_number": ["0272561313","416-272-2561","4162722561",null],
"zip_code": ["01001","55416","55416","22313-1450"],
"sales_tax_rate": [0.05,0.15,0.15,0.15],
"total_amount": [431.65,480.7,300.7,300.7]
}
)";
auto j = jsoncons::ojson::parse(jtext);
std::string output;
auto ioptions = csv::csv_options{}
.quote_style(csv::quote_style_kind::nonnumeric);
csv::encode_csv(j, output, ioptions);
std::cout << output << "\n\n";
auto ooptions = csv::csv_options{}
.assume_header(true)
.mapping_kind(csv::csv_mapping_kind::m_columns);
auto other = csv::decode_csv<jsoncons::ojson>(output, ooptions);
assert(other == j);
}
```
Output:
```
customer_name,has_coupon,phone_number,zip_code,sales_tax_rate,total_amount
"John Roe",true,"0272561313","01001",0.05,431.65
"Jane Doe",false,"416-272-2561","55416",0.15,480.7
"Joe Bloggs",false,"4162722561","55416",0.15,300.7
"John Smith",false,null,"22313-1450",0.15,300.7
```
<div id="eg4"/>
#### Encode a JSON array of objects to CSV with subfields
```cpp
#include <cassert>
#include <iostream>
#include <jsoncons/json.hpp>
#include <jsoncons_ext/csv/csv.hpp>
namespace csv = jsoncons::csv;
int main()
{
std::string jtext = R"(
[
{
"calculationPeriodCenters": ["NY","LON"],
"paymentCenters": "TOR",
"resetCenters": "LON"
},
{
"calculationPeriodCenters": "NY",
"paymentCenters": "LON",
"resetCenters": ["TOR","LON"]
},
{
"calculationPeriodCenters": ["NY","LON"],
"paymentCenters": "TOR",
"resetCenters": "LON"
},
{
"calculationPeriodCenters": "NY",
"paymentCenters": "LON",
"resetCenters": ["TOR","LON"]
}
]
)";
auto j = jsoncons::ojson::parse(jtext);
auto options = csv::csv_options{}
.subfield_delimiter(';');
std::string buf;
csv::encode_csv(j, buf, options);
std::cout << buf << "\n";
}
```
Output:
```
NY;LON,TOR,LON
NY,LON,TOR;LON
NY;LON,TOR,LON
NY,LON,TOR;LON
```
<div id="eg5"/>
#### Encode nested JSON to CSV (since 1.2.0)
```cpp
#include <cassert>
#include <iostream>
#include <jsoncons/json.hpp>
#include <jsoncons_ext/csv/csv.hpp>
namespace csv = jsoncons::csv;
int main()
{
std::string jtext = R"(
[
{
"text": "Chicago Reader",
"float": 1.0,
"datetime": "1971-01-01T04:14:00",
"boolean": true,
"nested": {
"time": "04:14:00",
"nested": {
"date": "1971-01-01",
"integer": 40
}
}
},
{
"text": "Chicago Sun-Times",
"float": 1.27,
"datetime": "1948-01-01T14:57:13",
"boolean": true,
"nested": {
"time": "14:57:13",
"nested": {
"date": "1948-01-01",
"integer": 63
}
}
}
]
)";
auto j = jsoncons::ojson::parse(jtext);
auto options = csv::csv_options{}
.flat(false);
std::string buf;
csv::encode_csv(j, buf, options);
std::cout << buf << "\n";
}
```
Output:
```
/text,/float,/datetime,/boolean,/nested/time,/nested/nested/date,/nested/nested/integer
Chicago Reader,1.0,1971-01-01T04:14:00,true,04:14:00,1971-01-01,40
Chicago Sun-Times,1.27,1948-01-01T14:57:13,true,14:57:13,1948-01-01,63
```
<div id="eg6"/>
#### Encode nested JSON to CSV with column mapping (since 1.2.0)
```cpp
#include <cassert>
#include <iostream>
#include <jsoncons/json.hpp>
#include <jsoncons_ext/csv/csv.hpp>
namespace csv = jsoncons::csv;
int main()
{
std::string jtext = R"(
[
{
"text": "Chicago Reader",
"float": 1.0,
"datetime": "1971-01-01T04:14:00",
"boolean": true,
"nested": {
"time": "04:14:00",
"nested": {
"date": "1971-01-01",
"integer": 40
}
}
},
{
"text": "Chicago Sun-Times",
"float": 1.27,
"datetime": "1948-01-01T14:57:13",
"boolean": true,
"nested": {
"time": "14:57:13",
"nested": {
"date": "1948-01-01",
"integer": 63
}
}
}
]
)";
auto j = jsoncons::ojson::parse(jtext);
auto options = csv::csv_options{}
.flat(false)
.column_mapping({
{"/datetime","Timestamp"},
{"/text", "Newspaper"},
{"/nested/nested/integer","Count"}
});
std::string buf;
csv::encode_csv(j, buf, options);
std::cout << buf << "\n";
}
```
Output:
```
Timestamp,Newspaper,Count
1971-01-01T04:14:00,Chicago Reader,40
1948-01-01T14:57:13,Chicago Sun-Times,63
```
|
