【Kotlin】Kotlin笔记11-Kotlin新特性(字符内嵌表达式,函数的参数默认值)

迷南。 2022-11-16 10:38 165阅读 0赞

### Kotlin笔记11-Kotlin新特性-字符内嵌表达式,函数的参数默认值 ###

**6. Kotlin新特性**

*  **字符内嵌表达式**

> **$**

<table> 
 <thead> 
  <tr> 
   <th>序号</th> 
   <th>Tips</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td>1</td> 
   <td>摆脱字符串联</td> 
  </tr> 
 </tbody> 
</table>

`内嵌表达式语法规则:`

class Obj {
        val name = ""
        val age = 0
    }
    "hello, ${obj.name}. nice to meet you!"

`仅有一个变量:`

"hello, $name. nice to meet you!"

`Example:`

val zero = "hello," + name + ".name to meet you." + " I'm " + age + " years old."

`内嵌表达式:`

val second = "hello, $name. nice to meet you!"

*  **函数的参数默认值**

<table> 
 <thead> 
  <tr> 
   <th>序号</th> 
   <th>Tips</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td>1</td> 
   <td>很大程度上能够代替构造函数</td> 
  </tr> 
 </tbody> 
</table>

`Example:设定参数默认值的方式:`

fun printParams(num: Int, str: String = "hello"){
    	println("num is $num , str is $str")
    }

`用法,注意对于第二个参数,可以传与不传,不传为默认值:`

printParams(123)

*特殊情况*  
`默认赋值第一个参数:`

fun printParams(num: Int = 100, str: String) {
    	print("num is $num ,  str is $str.")
    }

*  **Kotlin参数键值对机制**

<table> 
 <thead> 
  <tr> 
   <th>序号</th> 
   <th>Tips</th> 
  </tr> 
 </thead> 
 <tbody> 
  <tr> 
   <td>1</td> 
   <td>不必按照传统参数顺序赋值</td> 
  </tr> 
 </tbody> 
</table>

printParams(str = "world", num = 123)

`Example:`

fun printParams(num: Int = 100, str: String) {
    	print("num is $num ,  str is $str.")
    }
    
    fun main() {
    	printParams(str = "world")
    }

*次构造函数*

class Student(val sno: String, val grade: Int, name: String, age: Int) : Person(name, age){
    	constructor(name: String, age: Int) : this(" ",0, name, age) {}
    	constructor() : this(" ", 0)
    }

`采用参数默认值:`

class Student(val sno: String = "", val grade: Int = 0, name: String = "", age: Int = 0) : Person(name, age) {}