Swift - If...Else 语句

if语句后面可以跟一个可选的else语句，该语句在布尔表达式为 false 时执行。

句法

Swift 4 中if...else语句的语法如下 -

if boolean_expression {
   /* statement(s) will execute if the boolean expression is true */

} else {
   /* statement(s) will execute if the boolean expression is false */
}

如果布尔表达式的计算结果为true，则将执行if 代码块，否则将执行else 代码块。

例子

var varA:Int = 100;

/* Check the boolean condition using if statement */
if varA < 20 {
   /* If condition is true then print the following */
   print("varA is less than 20");

} else {
   /* If condition is false then print the following */
   print("varA is not less than 20");
}

print("Value of variable varA is \(varA)");

当上面的代码被编译并执行时，它会产生以下结果 -

varA is not less than 20
Value of variable varA is 100