kotlin内联函数——takeIf和takeUnless

1.takeIf

当对一个对象调用takeIf时，如果对象满足给定的判断条件，则返回该对象；否则，返回null。因此，takeIf是对单个对象进行过滤的函数。例如，

class User {
            var name: String? = null
            var age = 99
            fun set(ageParam: Int) {
                age = ageParam
            }

            fun get(): Int {
                return age
            }
        }     


 val user = User().takeIf {
            it.age == 99
        }
Log.d(TAG,"user对象:$user")

2.takeUnless

takeUnless的逻辑与takeIf相反。当对一个对象调用takeUnless时，如果对象满足给定的判断条件，则返回null；否则，返回该对象。例如，

class User {
            var name: String? = null
            var age = 99
            fun set(ageParam: Int) {
                age = ageParam
            }

            fun get(): Int {
                return age
            }
        }  


val user = User().takeUnless {
            it.age == 999
        }
Log.d(TAG,"user对象:$user")

注意：在takeIf和takeUnless函数调用后，如还有其他调用，请在调用时用？.判空。因为两者返回的对象可能为null。例如，

class User {
            var name: String? = null
            var age = 99
            fun set(ageParam: Int) {
                age = ageParam
            }

            fun get(): Int {
                return age
            }
        }  


Log.d(TAG, "User#age:${
                User().takeUnless {
                    it.age == 999
                }?.age
            }"
        )

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