How to correctly parse a JSON

[lbhack]

hi i want to access the field temp_C in json always getting empty value request using the code below :

/*

• NAppGUI Cross-platform C SDK
• 2015-2022 Francisco Garcia Collado
• MIT Licence
• https://nappgui.com/en/legal/license.html
• File: main.c

*/

/* NAppGUI Hello World */

#include "nappgui.h"
#include "inet.h"
#include "httpreq.h"
#include "json.h"

typedef struct _app_t App;
typedef struct _currentCondition_t CurrentCondition;
typedef struct WeatherDesc {
char_t value[20];
} WeatherDesc;

typedef struct WeatherIconUrl {
char_t value[100];
} WeatherIconUrl;

struct _currentCondition_t {
uint32_t FeelsLikeC;
uint32_t FeelsLikeF;
uint32_t cloudcover;
uint32_t humidity;
char_t localObsDateTime[20];
char_t observation_time[20];
real32_t precipInches;
real32_t precipMM;
uint32_t pressure;
real32_t pressureInches;
uint32_t temp_C;
uint32_t temp_F;
uint32_t uvIndex;
uint32_t visibility;
uint32_t visibilityMiles;
uint32_t weatherCode;
WeatherDesc weatherDesc[1];
WeatherIconUrl weatherIconUrl[1];
char_t winddir16Point[5];
uint32_t winddirDegree;
uint32_t windspeedKmph;
uint32_t windspeedMiles;
};

struct _app_t
{
Window *window;
TextView *text;

};
/---------------------------------------------------------------------------/

/---------------------------------------------------------------------------/

static void i_OnButton(App *app, Event *e)
{
Stream *gdata = NULL;
CurrentCondition *json=NULL;

Http *ht = http_secure("wttr.in",443);
if(http_get(ht, "/spain?format=j1", NULL, 0, NULL) == TRUE)
{
    //app->buff = str_printf("%d\n",http_response_status(ht));
    textview_printf(app->text, "%d\n",http_response_status(ht));
    gdata = stm_memory(4096);
    if (http_response_body(ht, gdata, NULL) == FALSE)
        stm_close(&gdata);
}
http_destroy(&ht);
dbind(CurrentCondition, uint32_t, temp_C);
json = json_read(gdata,NULL, CurrentCondition);
textview_printf(app->text,"The temp_c : %d\n",json->temp_C);
json_destroy(&json, CurrentCondition);
unref(e);

}
static Panel *i_panel(App *app)
{
Panel *panel = panel_create();
Layout *layout = layout_create(1, 3);
Label *label = label_create();
Button *button = button_push();
TextView *text = textview_create();
app->text = text;
label_text(label, "Hello!, I'm a label");
button_text(button, "Click Me!");
button_OnClick(button, listener(app, i_OnButton, App));
layout_label(layout, label, 0, 0);
layout_button(layout, button, 0, 1);
layout_textview(layout, text, 0, 2);
layout_hsize(layout, 0, 250);
layout_vsize(layout, 2, 200);
//layout_hsize(layout, 2, 200);
layout_margin(layout, 5);
layout_vmargin(layout, 0, 5);
layout_vmargin(layout, 1, 5);
panel_layout(panel, layout);
return panel;
}

/---------------------------------------------------------------------------/

static void i_OnClose(App *app, Event *e)
{
osapp_finish();
unref(app);
unref(e);
}

/---------------------------------------------------------------------------/

static App *i_create(void)
{
App *app = heap_new0(App);
Panel *panel = i_panel(app);
app->window = window_create(ekWINDOW_STD | ekWINDOW_RESIZE);
window_panel(app->window, panel);
window_title(app->window, "Hello, World!");
//window_size(app->window,s2df(800.0,400.0));
window_origin(app->window, v2df(500, 200));
window_OnClose(app->window, listener(app, i_OnClose, App));
window_show(app->window);
return app;
}

/---------------------------------------------------------------------------/

static void i_destroy(App **app)
{
window_destroy(&(*app)->window);
heap_delete(app, App);
}

/---------------------------------------------------------------------------/

#include "osmain.h"
osmain(i_create, i_destroy, "", App)

curl --silent wttr.in/spain?format=j1 | grep -i -o ""temp_c":.*[0-9]" --color=auto | sed 's/"//g'

[frang75]

Hi @lbhack !
Here is a small demo of how to correctly parse the JSON of your example.

/* NAppGUI Console Application */
    
#include "coreall.h"
#include "httpreq.h"
#include "json.h"
#include "inet.h"

/* Your C structs MUST follow the same organization as JSON, for automatic parsing. */
typedef struct _condition_t Condition;
typedef struct _weather_t Weather;

/* Every Condition has several fields, but we are only interested in 'temp_C' what is of string type */
struct _condition_t 
{
    String *temp_C;
};

/* SetUp arrays and sets for Condition structure */
DeclSt(Condition);

/* The global JSON has an ARRAY of objects of type Condition called 'current_condition' */
struct _weather_t
{
    ArrSt(Condition) *current_condition;
};

/*---------------------------------------------------------------------------*/

/* Data binding ONLY once when application starts */
/* https://nappgui.com/en/core/dbind.html */
/* https://nappgui.com/en/inet/json.html */
static void i_dbind(void)
{
    dbind(Condition, String*, temp_C);
    dbind(Weather, ArrSt(Condition)*, current_condition);
}

/*---------------------------------------------------------------------------*/

static Weather *i_get_weather(void)
{
    Weather *weather = NULL;

    Http *ht = http_secure("wttr.in",443);
    if(http_get(ht, "/madrid?format=j1", NULL, 0, NULL) == TRUE)
    {
        Stream *gdata = stm_memory(4096);
        if (http_response_body(ht, gdata, NULL) == TRUE)
        {
            /* We have the JSON string --> Parse to C Struct */
            weather = json_read(gdata, NULL, Weather);
        }

        /* ALWAYS you have to destroy the stream (not only if respose fails) */
        stm_close(&gdata);
    }
    
    http_destroy(&ht);
    return weather;
}

/*---------------------------------------------------------------------------*/

/* Console application created with */
/* commandApp("SimpleJson" "simplejson" "osapp;inet" NRC_PACKED) */
int main(int argc, char *argv[])
{
    uint32_t i = 0;
    unref(argc);
    unref(argv);
    core_start();
    inet_start();

    /* First, data binding, just once */
    i_dbind();

    for(i = 0; i < 10; ++i)
    {
        Weather *weather = i_get_weather();
        /* Weather can be obtained from REST-API */
        if (weather != NULL)
        {
            if(weather->current_condition != NULL)
            {
                /* We are interested in first element of 'current_condition' */
                if(arrst_size(weather->current_condition, Condition) > 0)
                {
                    const Condition *condition = arrst_first_const(weather->current_condition, Condition);
                    bstd_printf("temp_C: %s\n", tc(condition->temp_C));
                }
            }

            /* Data Binding knows how to completely destroy a binded object */
            /* https://nappgui.com/en/core/dbind.html#h4 */
            dbind_destroy(&weather, Weather);
        }
    }

    core_finish();
    inet_finish();
    return 0;
}

temp_C: 2
temp_C: 2
temp_C: 2
temp_C: 2
temp_C: 2
temp_C: 2
temp_C: 2
temp_C: 2
temp_C: 2
temp_C: 2
[23:20:21] [OK] Heap Memory Staticstics
[23:20:21] ============================
[23:20:21] Total a/dellocations: 273, 273
[23:20:21] Total bytes a/dellocated: 1300184, 1300184
[23:20:21] Max bytes allocated: 108676
[23:20:21] Effective reallocations: (0/0)
[23:20:21] Real allocations: 2 pages of 65536 bytes
[23:20:21]                   10 pages greater than 65536 bytes
[23:20:21] ============================
[23:20:21] Config: Debug

[lbhack]

mucha gracias

[lbhack]

hi and if i want to access the array country from array nearest_area what i need to change ?

[frang75]

I'm sure you can do it yourself, following the example I gave you.

[lbhack]

ok thanks i get it .

[lbhack]

here i finished the mini project with code about Weather Information :

/*

• NAppGUI Cross-platform C SDK
• 2015-2022 jose jaramillo
• MIT Licence
• File: main.c

*/

/* NAppGUI Weather Info */

#include "nappgui.h"
#include "inet.h"
#include "httpreq.h"
#include "json.h"
/* Define App struct, which contains the main window, text view, and other elements /
typedef struct _app_t App;
/ Your C structs MUST follow the same organization as JSON, for automatic parsing. /
typedef struct _condition_t Condition;
typedef struct _weather_t Weather;
typedef struct val Values;
typedef struct nearest_area Nearestarea;
typedef struct count Country;
/ Every Condition has several fields, but we are only interested in 'temp_C' what is of string type */
struct count
{
String *value; //value of country
};
struct val
{
String *value; // value Weather description
};
struct _condition_t
{
String *pressure;
String *temp_F;
String *temp_C;
ArrSt(Values) *weatherDesc;

};
struct nearest_area
{
ArrSt(Country) *country;
};

/* SetUp arrays and sets for Condition structure /
DeclSt(Condition);
DeclSt(Values);
DeclSt(Nearestarea);
DeclSt(Country);
/ The global JSON has an ARRAY of objects of type Condition called 'current_condition' */
struct _weather_t
{
// ArrSt(Condition) *nearest_area;
ArrSt(Condition) *current_condition;
ArrSt(Nearestarea) *nearest_area;

};

struct _app_t
{
Window *window;
TextView *text;
String *lop;
String count;
Edit country;
};
/---------------------------------------------------------------------------/

static void init_bind()
{

dbind(Condition, String*, temp_C);
dbind(Condition, String*, pressure);
dbind(Condition, String*, temp_F);
dbind(Values, String*, value);
dbind(Condition, ArrSt(Values)* , weatherDesc);
dbind(Weather, ArrSt(Condition)*, current_condition);
dbind(Country, String*, value);
dbind(Nearestarea, ArrSt(Country)*, country);
dbind(Weather, ArrSt(Nearestarea)*, nearest_area);


/*---------------------------------------------------------------------------*/

}
static uint32_t i_OnButton(App *app)
{
Stream *gdata = NULL;
Weather *weather = NULL;;
String *path;

Http *ht = http_secure("wttr.in",443);
path = str_printf("/%s?format=j1",app->count);
if(http_get(ht, tc(path), NULL, 0, NULL) == TRUE)
{
    gdata = stm_memory(4096);
    if (http_response_body(ht, gdata, NULL) == FALSE)
        stm_close(&gdata);
}
http_destroy(&ht);

weather = json_read(gdata,NULL, Weather);
stm_close(&gdata);


        /* Weather can be obtained from REST-API */
        if (weather != NULL)
        {
            if(weather->current_condition != NULL)
            {
                if(arrst_size(weather->current_condition,Condition) > 0)
                {
                    const Condition *condition = arrst_first_const(weather->current_condition, Condition);
                    const Values *weatherDesc2 = arrst_first_const(condition->weatherDesc, Values);
                       const Nearestarea *near = arrst_first_const(weather->nearest_area,Nearestarea);
                       const Country *counname = arrst_first_const(near->country, Country);

                    
app->lop = str_printf("\n City name : %s\n\n --------------- \n\n    pressure : %s \n  temp_C : %s \n  temp_F : %s \n weatherDesc: %s  \n Country : %s \n ---------------- ",app->count, tc(condition->pressure),tc(condition->temp_C),tc(condition->temp_F),tc(weatherDesc2->value),tc(counname->value));

                  
                }
               
            }
    
           
            
            dbind_destroy(&weather, Weather);
        }

return 0;

}
static void end_t(App *app,uint32_t rvalue)
{
if (rvalue == 0)
{
textview_printf(app->text,"%s\n",app->lop->data);
edit_text(app->country,"");
textview_scroll_down(app->text);
str_destroy(&app->lop);
}
}
static void bt(App *app,Event *e)
{
textview_clear(app->text);
app->count = edit_get_text(app->country);
osapp_task(app,0,i_OnButton,NULL,end_t,App);
unref(e);
}
static void ex(App *app,Event *e)
{
osapp_finish();
unref(app);
unref(e);

}
static Panel *i_panel(App *app)
{
Panel *panel = panel_create();
Layout *layout = layout_create(1, 5);
Label *desc = label_create();
Button *button = button_push();
Button *Exit = button_push();
TextView *text = textview_create();
app->country = edit_create();
app->text = text;
button_text(button, "Get Weather");
button_text(Exit, "Exit");
label_text(desc, "Enter Country or City Then Press Enter :");
button_OnClick(button, listener(app, bt, App));
button_OnClick(Exit, listener(app, ex, App));
textview_color(app->text, kCOLOR_GREEN);
textview_halign(app->text, ekCENTER);
textview_size(app->text, s2df(30.0, 30.0));
label_color(desc,kCOLOR_YELLOW);
layout_label(layout, desc, 0, 0);
layout_edit(layout, app->country, 0, 1);
layout_button(layout, button, 0, 2);
layout_button(layout, Exit, 0, 3);
layout_textview(layout, text, 0, 4);
layout_hsize(layout, 0, 250);
layout_vsize(layout, 4, 200);
layout_margin(layout, 5);
layout_vmargin(layout, 0, 5);
layout_vmargin(layout, 2, 5);
layout_vmargin(layout, 2, 5);
layout_vmargin(layout, 1, 5);
panel_layout(panel, layout);
init_bind();
return panel;
}

/---------------------------------------------------------------------------/

static void i_OnClose(App *app, Event *e)
{
bool_t *result = event_result(e, bool_t);
*result = FALSE;
bt(app,ekFOK);
unref(app);
unref(e);

}

/---------------------------------------------------------------------------/

static App *i_create(void)
{
App *app = heap_new0(App);
Panel *panel = i_panel(app);
app->window = window_create(ekWINDOW_TITLE | ekWINDOW_RETURN);
window_panel(app->window, panel);
window_title(app->window, "Weather info");
window_origin(app->window, v2df(500, 200));
window_OnClose(app->window, listener(app, i_OnClose, App));
window_show(app->window);
return app;
}

/---------------------------------------------------------------------------/

static void i_destroy(App **app)
{
window_destroy(&(*app)->window);
heap_delete(app, App);
}

/---------------------------------------------------------------------------/

#include "osmain.h"
osmain(i_create, i_destroy, "", App)

[lbhack]

[frang75]

Hi @lbhack !
That's looks good!
Congratulations on completing your first NAppGUI project.

[frang75]

Improved Json documentation:
https://nappgui.com/en/inet/json.html
https://nappgui.com/en/howto/htjson.html