[Variable Scope & Qualifiers]
描述
The static
keyword is used to create variables that are visible to only one function. However unlike local variables that get created and destroyed every time a function is called, static variables persist beyond the function call, preserving their data between function calls.
Variables declared as static will only be created and initialized the first time a function is called.
範例程式碼
/* RandomWalk * Paul Badger 2007 * RandomWalk wanders up and down randomly between two * endpoints. The maximum move in one loop is governed by * the parameter "stepsize". * A static variable is moved up and down a random amount. * This technique is also known as "pink noise" and "drunken walk". */ #define randomWalkLowRange -20 #define randomWalkHighRange 20 int stepsize; int thisTime; int total; void setup() { Serial.begin(9600); } void loop() { // tetst randomWalk function stepsize = 5; thisTime = randomWalk(stepsize); Serial.println(thisTime); delay(10); } int randomWalk(int moveSize){ static int place; // variable to store value in random walk - declared static so that it stores // values in between function calls, but no other functions can change its value place = place + (random(-moveSize, moveSize + 1)); if (place < randomWalkLowRange){ // check lower and upper limits place = place + (randomWalkLowRange - place); // reflect number back in positive direction } else if(place > randomWalkHighRange){ place = place - (place - randomWalkHighRange); // reflect number back in negative direction } return place; }
語法參考主頁面
86Duino 參考的文本是根據 Creative Commons Attribution-ShareAlike 3.0 License,部分文本是從 the Arduino reference 修改的。 參考中的代碼示例已發佈到公共領域。