将变量从一个函数解析到另一个函数

Question

我有一个从Web服务接收UID的函数，我需要它将该字符串传递给函数中断，该函数中断在按下按钮后将请求发送回具有匹配UID的服务器。

如何从一个函数到另一个函数获取字符串？

const int buttonPin = D1;
const int ledPin = 13;

void fire(void);
volatile int state = LOW;

//#include <string.h>
char server[] = "xxxxxxxx.com";
TCPClient client;

// name the pins
int red = D3; //RED
int green = D4; //AMBER
int pinCommand;

void setup() {
//Register our Spark function here
Spark.function("led", ledControl);

for (int pin = D3; pin <= D4; ++pin) {
    pinMode(pin, OUTPUT);
    digitalWrite(pin, LOW);
}
//set RED (D3) LED state to on
digitalWrite(D3, HIGH);
pinMode(buttonPin, INPUT);
attachInterrupt(D1, fire, CHANGE);

Serial.begin(9600);
}

int ledControl(String command) {

//find out the pin number and convert the ascii to integer
int pinCommand = (command.charAt(0) - '0');
String UID = command.substring(2,8);
if ((pinCommand = 1)) {
    // GREEN (D5) LED TO ON, RED (D3) LED TO OFF
    digitalWrite(D4, HIGH);
    digitalWrite(D3, LOW);
}

else {
    //GREEN (D5) LED TO OFF, RED (D3) LED TO On
    digitalWrite(D4, LOW);
    digitalWrite(D3, HIGH);
    Serial.println("Fail");
}
return 1;
}

void loop() {

}

void fire() {

if (digitalRead(D4) == HIGH) {
    state = !state;
    if (client.connect(server, 80)) {
            Serial.println("connected");
            client.println("POST /deployapp/"+UID+" HTTP/1.1");
            Serial.println(UID);
            client.print("Host: ");
            client.println(server);
            client.println("Accept: text/html, text/plain");
            client.println();
            client.flush();
        }

        else {    
            Serial.println("connection failed");
            client.stop();
        }
}

else {
    Serial.println("AUTHENTICATE FIRST");
    }
}