解析GET响应

Question

我无法从GET响应中提取需要的数据 我只想记住介于“ - ”和“ - ”之间的charcaters，因为我不需要其他任何东西。我试图用一个while循环，如下图所示，但它不会工作

谢谢

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，在这里，你有不同的问题。

1. 您不能比较字符（c）和字符串（"-"）。您应该使用'-'与char进行比较。
2. 虽然在你的循环将阻止程序执行。你应该使用一种状态机（例如使用一个状态变量）。
3. 如果您正确书写阅读功能，则无需使用substring函数。在任何情况下，substring函数都需要INDICES，而不是字符。

这就是说，该代码应工作你的情况：

// 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"); 
} 

不管怎样，我真的不喜欢的Arduino使用可变大小的变量，因为你有很少的内存（为什么你应该浪费？）。我的建议是总是使用固定大小的字符串（又名字符数组）。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"); 
} 

编辑：

的OP提到，字符串不是由两个分隔了“ - ”，而是他们“<”和“>”之间封闭。

的代码，因此，应该以这种方式修改：

// 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"); 
}