我在调用我所构造的构造函数内部的方法时遇到问题。这是函数和我尝试调用它...
var Cohort = function(program, campus, number, students){
this.program = program,
this.campus = campus,
this.number = number,
this.students = students,
function sayName(){
return `This cohort is called ${program}, ${campus}, ${number}.`
},
function takeAttendance(){
return console.log(students)
}
}
var cohort1 = new Cohort("w", "pr", 27, ['devin', 'ben', 'bob'])
var cohort2 = new Cohort('w', 'pr', 31, ["Brendan Eich", "Dan Abramov", "Wes Bos", "Kent Dodds"])
cohort1.sayName()
控制台说cohort1.sayName不是函数。
答案 0 :(得分：3)
您必须将方法设置到原型上。您在代码中所做的只是声明Cohort函数范围的本地函数，因此它们不是方法。
每当您致电new Cohort(...)时，对象都会被new Cohort().__proto__ === Cohort.prototype链接起来Cohort.prototype，而this会成为新Cohort对象的Cohort.prototype.methods。属性将保存到。设置Cohort使用原型链逻辑允许在var Cohort = function(program, campus, number, students) {
this.program = program
this.campus = campus
this.number = number
this.students = students
}
Cohort.prototype.sayName = function() {
return `This cohort is called ${this.program}, ${this.campus}, ${this.number}.`
}
Cohort.prototype.takeAttendance = function() {
return console.log(this.students)
}
var cohort1 = new Cohort("w", "pr", 27, ['devin', 'ben', 'bob'])
var cohort2 = new Cohort('w', 'pr', 31, ["Brendan Eich", "Dan Abramov", "Wes Bos", "Kent Dodds"])
console.log(cohort1.sayName())
cohort1.takeAttendance()
console.log(Object.getOwnPropertyNames(cohort1))
console.log(Object.getOwnPropertyNames(cohort1.__proto__))对象的每个实例上调用这些方法
class Cohort {
constructor(program, campus, number, students) {
this.program = program
this.campus = campus
this.number = number
this.students = students
}
sayName() {
return `This cohort is called ${this.program}, ${this.campus}, ${this.number}.`
}
takeAttendance() {
return console.log(this.students)
}
}
var cohort1 = new Cohort("w", "pr", 27, ['devin', 'ben', 'bob'])
var cohort2 = new Cohort('w', 'pr', 31, ["Brendan Eich", "Dan Abramov", "Wes Bos", "Kent Dodds"])
console.log(cohort1.sayName())
cohort1.takeAttendance()
console.log(Object.getOwnPropertyNames(cohort1))
console.log(Object.getOwnPropertyNames(cohort1.__proto__))
在ES6中，您只需执行
即可
class
这个console.log构造实际上只是一个与ES5实现相同逻辑的语法糖
作为额外注释，以下代码也有效，但通常不是首选。注意方法存储位置的不同（检查最后2 var Cohort = function(program, campus, number, students) {
this.program = program
this.campus = campus
this.number = number
this.students = students
this.sayName = function() {
return `This cohort is called ${this.program}, ${this.campus}, ${this.number}.`
}
this.takeAttendance = function() {
return console.log(this.students)
}
}
var cohort1 = new Cohort("w", "pr", 27, ['devin', 'ben', 'bob'])
var cohort2 = new Cohort('w', 'pr', 31, ["Brendan Eich", "Dan Abramov", "Wes Bos", "Kent Dodds"])
console.log(cohort1.sayName())
cohort1.takeAttendance()
console.log(Object.getOwnPropertyNames(cohort1))
console.log(Object.getOwnPropertyNames(cohort1.__proto__))并与上面的方法进行比较）
webView.scrollView.contentInsetAdjustmentBehavior = .never
答案 1 :(得分：1)
要在函数内部使用函数，必须使用与分配属性相同的方式进行分配。
您可以通过添加SELECT district_name,
sum("Population") as total,
sum(CASE WHEN "Cluster" IN ('city', 'town')
THEN "Population"
ELSE 0
END ) as district_total,
sum(CASE WHEN "Cluster" IN ('city', 'town')
THEN "Population"
ELSE 0
END ) * 100.0 / sum("Population") as PP
FROM residentioal
GROUP BY district_name;
：
this ...或使用var Cohort = function(program, campus, number, students) {
this.program = program
this.campus = campus
this.number = number
this.students = students
this.sayName = function() {
return `This cohort is called ${this.program}, ${this.campus}, ${this.number}.`
}
this.takeAttendance = function() {
return console.log(students)
}
}
var cohort1 = new Cohort("w", "pr", 27, ['devin', 'ben', 'bob'])
var cohort2 = new Cohort('w', 'pr', 31, ["Brendan Eich", "Dan Abramov", "Wes Bos", "Kent Dodds"])
console.log(cohort1.sayName())
（大多数开发人员的首选方法）：
prototype