解析GET響應

Question

我無法從GET響應中提取需要的數據 我只想記住介於「 - 」和「 - 」之間的charcaters，因爲我不需要其他任何東西。我試圖用一個while循環，如下圖所示，但它不會工作

謝謝

String readString; 

    while (client.connected() || client.available()) { 
     char c = client.read(); //gets byte from ethernet buffer 

     while(c != "-"); //this throw error 
     readString += c; //places captured byte in readString 
    } 

    client.stop(); //stop client 

    Serial.print(readString); 

    String res = readString.substring("-","-"); //throw error 
    String val = "happy"; 

    if(res == val){ 
     Serial.print(res); 
     Serial.println(" happy"); 
    }else{ 
     Serial.print(res); 
     Serial.println(" sad"); 
    } 

    Serial.println("=================="); 
    Serial.println(); 
    readString=""; //clear readString variable 

Answer 1

好了，在這裏，你有不同的問題。

1. 您不能比較字符（c）和字符串（"-"）。您應該使用'-'與char進行比較。
2. 雖然在你的循環將阻止程序執行。你應該使用一種狀態機（例如使用一個狀態變量）。
3. 如果您正確書寫閱讀功能，則無需使用substring函數。在任何情況下，substring函數都需要INDICES，而不是字符。

這就是說，該代碼應工作你的情況：

// state = 
// 0 -> waiting for first - 
// 1 -> reading the answer and waiting for second - 
// 2 -> finished reading 
uint8_t state = 0; 

while (client.connected() || client.available()) { 
    char c = client.read(); //gets byte from ethernet buffer 

    if ((c == '-') && (state < 2)) 
     state++; 
    if ((state == 1) && (c != '-')) 
     readString += c; 
} 

client.stop(); //stop client 

Serial.print(readString); 
String val = "happy"; 

if(res == val){ 
    Serial.print(readString); 
    Serial.println(" happy"); 
}else{ 
    Serial.print(readString); 
    Serial.println(" sad"); 
} 

不管怎樣，我真的不喜歡的Arduino使用可變大小的變量，因爲你有很少的內存（爲什麼你應該浪費？）。我的建議是總是使用固定大小的字符串（又名字符數組）。例如：

// state = 
// 0 -> waiting for first - 
// 1 -> reading the answer and waiting for second - 
// 2 -> finished reading 
uint8_t state = 0; 

char readString[MAX_SIZE+1]; 
uint8_t readStringIndex = 0; 

while (client.connected() || client.available()) { 
    char c = client.read(); //gets byte from ethernet buffer 

    if ((c == '-') && (state < 2)) 
     state++; 
    if ((state == 1) && (c != '-')) 
    { 
     readString[readStringIndex] = c; 
     readStringIndex++; 
    } 
} 
readString[readStringIndex] = '\0'; // string terminator 

client.stop(); //stop client 

Serial.print(readString); 

if(strcmp(readString, "happy")){ 
    Serial.print(readString); 
    Serial.println(" happy"); 
}else{ 
    Serial.print(readString); 
    Serial.println(" sad"); 
} 

編輯：

的OP提到，字符串不是由兩個分隔了「 - 」，而是他們「<」和「>」之間封閉。

的代碼，因此，應該以這種方式修改：

// state = 
// 0 -> waiting for first - 
// 1 -> reading the answer and waiting for second - 
// 2 -> finished reading 
uint8_t state = 0; 

char readString[MAX_SIZE+1]; 
uint8_t readStringIndex = 0; 

while (client.connected() || client.available()) { 
    char c = client.read(); //gets byte from ethernet buffer 

    switch (state) 
    { 
     case 0: // Waiting for first char 
      if (c == '<') 
       state = 1; 
      break; 
     case 1: // Reading the answer and waiting for second char 
      if (c == '>') 
       state = 2; 
      else 
      { 
       readString[readStringIndex] = c; 
       readStringIndex++; 
      } 
      break; 
    } 
} 
readString[readStringIndex] = '\0'; // string terminator 

client.stop(); //stop client 

Serial.print(readString); 

if(strcmp(readString, "happy")){ 
    Serial.print(readString); 
    Serial.println(" happy"); 
}else{ 
    Serial.print(readString); 
    Serial.println(" sad"); 
}