从API获取UYU汇率

Question

我有这个函数，应该从下一页中提取汇率并将其作为值返回。问题是由于某种原因我不知道它无法捕获该值。

double getExchangeRate()
{
    CURL *curl;
    CURLcode res;
    struct MemoryStruct chunk;
    chunk.memory = malloc(1);
    chunk.size = 0;

    double exchangeRate = 0.0;

    curl_global_init(CURL_GLOBAL_DEFAULT);
    curl = curl_easy_init();
    if (curl)
    {
        curl_easy_setopt(curl, CURLOPT_URL, "https://open.er-api.com/v6/latest/USD");
        curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, WriteMemoryCallback);
        curl_easy_setopt(curl, CURLOPT_WRITEDATA, (void *)&chunk);
        curl_easy_setopt(curl, CURLOPT_FOLLOWLOCATION, 1L);

        // Make the request
        res = curl_easy_perform(curl);
        if (res != CURLE_OK)
        {
            fprintf(stderr, "curl_easy_perform() falue: %s\n", curl_easy_strerror(res));
        }
        else
        {
            printf("Response length: %zu\n", chunk.size);
            printf("API response: %s\n", chunk.memory);

            // Find the UYU exchange rate in the answer
            char *start = strstr(chunk.memory, "\"UYU\":");
            if (start)
            {
                start += 6; // Move the pointer after "\"UYU\":"
                exchangeRate = strtod(start, &start); //
                printf("Exchange rate obtained: %.2f\n", exchangeRate);
            }
            else
            {
                printf("The UYU exchange rate was not found in the response.\n");
            }
        }
        free(chunk.memory);
        curl_easy_cleanup(curl);
    }
    curl_global_cleanup();

    return exchangeRate;
}

Answer 1

因为您只显示了代码的一部分...这是一个检索和扫描速率的简单示例，如果找到则打印

#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <curl/curl.h>

char resultsBuff[8192*4] = {0}; // Buffer for response, populated in the callback fn

size_t callbackWr(void *contents, size_t size, size_t nmemb, void *userp) {
    size_t total_size = size * nmemb;
    char *buffer = (char *)userp;
    strncat(buffer, (char *)contents, total_size);
    return total_size;
}

void scanResults( char *curr )
{
    char currBuff[80];
    char *start;
    char *endOf;
    char *rates;
    char thisRate[80];

    rates = strstr( resultsBuff, "\"rates\":" );//scan only the 'rates' bit
    if ( rates == NULL )
    {
        fprintf(stderr, "no rates found in [%s]\n", resultsBuff );
    exit(1);
    }
    
    sprintf(currBuff, "\"%s\"", curr );
    start = strstr(rates, currBuff);
    if ( start )
    {
        endOf=strstr(start, "," );
    if ( endOf == NULL )
            endOf=strstr(start, "}" );   // if its the last currency ...
    
    if ( endOf != NULL )
        strncpy( thisRate, start, endOf - start );
    }

    if ( start == NULL || endOf == NULL )
        fprintf( stderr, "no exchange rate found for [%s]\n", curr );
    else
    printf( "%s\n", thisRate );
}

int main( int argc, char **argv )
{
    char currency[20];
    CURL *curl;
    CURLcode res;

    if ( argc == 2 )
        strcpy( currency, argv[1] );
    else{
    printf( "usage: %s currency\n", argv[0] );
    exit(1);
    }

    curl = curl_easy_init();
    if(curl) {
        curl_easy_setopt(curl, CURLOPT_URL, "https://open.er-api.com/v6/latest/USD");
        curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, callbackWr );
        curl_easy_setopt(curl, CURLOPT_WRITEDATA, resultsBuff);

        res = curl_easy_perform(curl);

        if(res != CURLE_OK)
            fprintf(stderr, "Request failed: %s\n", curl_easy_strerror(res));
        else
            scanResults( currency ); // print if a rate exists for this currency
        
        curl_easy_cleanup(curl);
    }
    return 0;
}


# running that against the following
for rate in XDF XPF YER ZAR USD GBP YEN JPY BSD USD AZN GIP HKD
do
./curly $rate
done
no exchange rate found for [XDF]
"XPF":113.645236
"YER":249.782528
"ZAR":18.148279
"USD":1
"GBP":0.789701
no exchange rate found for [YEN]
"JPY":149.715109
"BSD":1
"USD":1
"AZN":1.700218
"GIP":0.789699
"HKD":7.781721