Solidity – while循环

语法

Solidity 中， while循环的语法如下：

while 表达式) {
   被执行语句如果表示为真)
}

示例

pragma solidity ^0.5.0;

contract SolidityTest {
   uint storedData; 
   constructor) public{
      storedData = 10;   
   }
   function getResult) public view returnsstring memory){
      uint a = 10; 
      uint b = 2;
      uint result = a + b;
      return integerToStringresult); 
   }
   function integerToStringuint _i) internal pure 
      returns string memory) {

      if _i == 0) {
         return "0";
      }
      uint j = _i;
      uint len;

      while j != 0) {
         len++;
         j /= 10;
      }
      bytes memory bstr = new byteslen);
      uint k = len - 1;

      while _i != 0) { // while 循环
         bstr[k--] = byteuint848 + _i % 10));
         _i /= 10;
      }
      return stringbstr);
   }
}

Solidity – do…while循环

语法

Solidity 中， do…while循环的语法如下：

do {
   被执行语句如果表示为真)
} while 表达式);

注意: 不要漏掉do后面的分号。

示例

pragma solidity ^0.5.0;

contract SolidityTest {
   uint storedData; 
   constructor) public{
      storedData = 10;   
   }
   function getResult) public view returnsstring memory){
      uint a = 10; 
      uint b = 2;
      uint result = a + b;
      return integerToStringresult); 
   }
   function integerToStringuint _i) internal pure 
      returns string memory) {

      if _i == 0) {
         return "0";
      }
      uint j = _i;
      uint len;

      while j != 0) {
         len++;
         j /= 10;
      }
      bytes memory bstr = new byteslen);
      uint k = len - 1;

      do {                   // do while 循环 
         bstr[k--] = byteuint848 + _i % 10));
         _i /= 10;
      }
      while _i != 0);
      return stringbstr);
   }
}

Solidity – for循环

语法

Solidity 中， for循环的语法如下：

for 初始化; 测试条件; 迭代语句) {
   被执行语句如果表示为真)
}

示例

pragma solidity ^0.5.0;

contract SolidityTest {
   uint storedData; 
   constructor) public{
      storedData = 10;   
   }

   function getResult) public view returnsstring memory){
      uint a = 10; 
      uint b = 2;
      uint result = a + b;
      return integerToStringresult); 
   }

   function integerToStringuint _i) internal pure 
      returns string memory) {
      if _i == 0) {
         return "0";
      }
      uint j=0;
      uint len;
      for j = _i; j != 0; j /= 10) {  //for循环的例子
         len++;         
      }
      bytes memory bstr = new byteslen);
      uint k = len - 1;
      while _i != 0) {
         bstr[k--] = byteuint848 + _i % 10));
         _i /= 10;
      }
      return stringbstr);//访问局部变量
   }
}

Solidity – break与contin

continue – 跳出本次循环，继续执行接下来的循环
break – 跳出循环或跳出代码块)

break 示例

pragma solidity ^0.5.0;

contract SolidityTest {
   uint storedData; 
   constructor) public{
      storedData = 10;   
   }
   function getResult) public view returnsstring memory){
      uint a = 1; 
      uint b = 2;
      uint result = a + b;
      return integerToStringresult); 
   }
   function integerToStringuint _i) internal pure 
      returns string memory) {

      if _i == 0) {
         return "0";
      }
      uint j = _i;
      uint len;

      while true) {
         len++;
         j /= 10;
         ifj==0){
            break;   // break 语句跳出循环
         }
      }
      bytes memory bstr = new byteslen);
      uint k = len - 1;

      while _i != 0) {
         bstr[k--] = byteuint848 + _i % 10));
         _i /= 10;
      }
      return stringbstr);
   }
}

输出

0: string: 3

continue 示例

pragma solidity ^0.5.0;

contract SolidityTest {
   uint storedData; 
   constructor) public{
      storedData = 10;   
   }
   function getResult) public view returnsstring memory){
      uint n = 1;
      uint sum = 0;

      while n < 10){
         n++;
         ifn == 5){
            continue; // 当n的和是5时，跳过n。
         }
         sum = sum + n;
      }
      return integerToStringsum); 
   }
   function integerToStringuint _i) internal pure 
      returns string memory) {

      if _i == 0) {
         return "0";
      }
      uint j = _i;
      uint len;

      while true) {
         len++;
         j /= 10;
         ifj==0){
            break;   // break跳出循环
         }
      }
      bytes memory bstr = new byteslen);
      uint k = len - 1;

      while _i != 0) {
         bstr[k--] = byteuint848 + _i % 10));
         _i /= 10;
      }
      return stringbstr);
   }
}