无涯教程-Dart - 循环语句下图说明了条件循环的分类- Sr.No Loop & Remark 1 for

下图说明了条件循环的分类-

Sr.No	Loop & Remark
1	for loop for 循环是确定循环的实现， for循环将代码块执行指定的次数，它可以用于迭代一组固定值，如数组
2	for…in Loop for ... in循环用于循环访问对象的属性。

继续，让我们现在讨论无限循环，当循环中的迭代次数不确定或未知时，将使用不确定循环，无限循环可以使用-

Sr.No	Loop & Remark
1	while Loop 每当指定的条件求值为true时，while循环就会执行指令。换句话说，循环在执行代码块之前先判断条件。
2	do…while Loop do ... while循环与while循环类似，不同之处在于do ... while循环在第一次执行循环时不会判断条件。

现在让我们继续讨论Dart的循环控制语句。

Sr.No	Control Statement & Remark
1	break Statement break 语句用于将控件移出构造。在循环中使用 break 会使程序退出循环。以下是 break 语句的Example。
2	continue Statement continue 语句跳过当前迭代中的后续语句，并将控制权带回到循环的开始。

标签控制

标签只是一个标识符，后跟一个冒号(:)，该冒号用于语句或代码块，标签可以与 break 和 continue 一起使用，以更精确地控制流量。

在continue或break语句及其标签名称之间不允许使用换行符，同样，在标签名称和关联的循环之间不应有任何其他语句。

示例 - Break

void main() { 
   outerloop: //这是标签名称
for (var i=0; i < 5; i++) {
print("Innerloop: ${i}");
innerloop:
  </span><span class="kwd">for</span><span class="pln"> </span><span class="pun">(</span><span class="kwd">var</span><span class="pln"> j</span><span class="pun">=</span><span class="lit">0</span><span class="pun">;</span><span class="pln"> j </span><span class="pun">&lt;</span><span class="pln"> </span><span class="lit">5</span><span class="pun">;</span><span class="pln"> j</span><span class="pun">++)</span><span class="pln"> </span><span class="pun">{</span><span class="pln"> 
     </span><span class="kwd">if</span><span class="pln"> </span><span class="pun">(</span><span class="pln">j </span><span class="pun">&gt;</span><span class="pln"> </span><span class="lit">3</span><span class="pln"> </span><span class="pun">)</span><span class="pln"> </span><span class="kwd">break</span><span class="pln"> </span><span class="pun">;</span><span class="pln"> 
     
     </span><span class="com">//退出最里面的循环</span><span class="pln">
     </span><span class="kwd">if</span><span class="pln"> </span><span class="pun">(</span><span class="pln">i </span><span class="pun">==</span><span class="pln"> </span><span class="lit">2</span><span class="pun">)</span><span class="pln"> </span><span class="kwd">break</span><span class="pln"> innerloop</span><span class="pun">;</span><span class="pln"> 
     
     </span><span class="com">//跟上面一样</span><span class="pln">
     </span><span class="kwd">if</span><span class="pln"> </span><span class="pun">(</span><span class="pln">i </span><span class="pun">==</span><span class="pln"> </span><span class="lit">4</span><span class="pun">)</span><span class="pln"> </span><span class="kwd">break</span><span class="pln"> outerloop</span><span class="pun">;</span><span class="pln"> 
     
     </span><span class="com">//退出外循环</span><span class="pln">
     </span><span class="kwd">print</span><span class="pun">(</span><span class="str">"Innerloop: ${j}"</span><span class="pun">);</span><span class="pln"> 
  </span><span class="pun">}</span><span class="pln"> 

}
}

成功执行上述代码后，将显示以下输出。

Innerloop: 0
Innerloop: 0
Innerloop: 1
Innerloop: 2
Innerloop: 3
Innerloop: 1
Innerloop: 0
Innerloop: 1
Innerloop: 2
Innerloop: 3
Innerloop: 2
Innerloop: 3
Innerloop: 0
Innerloop: 1
Innerloop: 2
Innerloop: 3
Innerloop: 4

示例 - Continue

void main() { 
   outerloop: //这是标签名称
for (var i=0; i < 3; i++) {
print("Outerloop:${i}");
  </span><span class="kwd">for</span><span class="pln"> </span><span class="pun">(</span><span class="kwd">var</span><span class="pln"> j</span><span class="pun">=</span><span class="lit">0</span><span class="pun">;</span><span class="pln"> j </span><span class="pun">&lt;</span><span class="pln"> </span><span class="lit">5</span><span class="pun">;</span><span class="pln"> j</span><span class="pun">++)</span><span class="pln"> </span><span class="pun">{</span><span class="pln"> 
     </span><span class="kwd">if</span><span class="pln"> </span><span class="pun">(</span><span class="pln">j </span><span class="pun">==</span><span class="pln"> </span><span class="lit">3</span><span class="pun">){</span><span class="pln"> 
        </span><span class="kwd">continue</span><span class="pln"> outerloop</span><span class="pun">;</span><span class="pln"> 
     </span><span class="pun">}</span><span class="pln"> 
     </span><span class="kwd">print</span><span class="pun">(</span><span class="str">"Innerloop:${j}"</span><span class="pun">);</span><span class="pln"> 
  </span><span class="pun">}</span><span class="pln"> 

}
}

成功执行上述代码后，将显示以下输出。

Outerloop: 0 
Innerloop: 0 
Innerloop: 1 
Innerloop: 2 
Outerloop: 1
Innerloop: 0
Innerloop: 1
Innerloop: 2
Outerloop: 2
Innerloop: 0
Innerloop: 1
Innerloop: 2

无涯教程-Dart - 循环语句

标签控制

示例 - Break

示例 - Continue

参考链接