/*
for循环
格式: for (初始化表达式;循环保持条件;循环后表达式) {需要执行的语句}
OC:
int sum = 0;
for (int i = 0; i <= 10; i++) {
sum = i++;
}
NSLog(@"%d", sum);
int sum = 0;
int i = 0;
for (; i <= 10; i++) {
sum = i++;
}
NSLog(@"%d", sum);
int sum = 0;
int i = 0;
for (; i <= 10; ) {
sum = i++;
i++;
}
NSLog(@"%d", sum);
int sum = 0;
int i = 0;
for ( ; ; ) {
sum = i++;
i++;
if (i > 10) {
break;
}
}
NSLog(@"%d", sum);
int sum = 0;
int i = 0;
for ( ; ; ) {
sum = i++;
i++;
NSLog(@"%d", sum);
}
如果只有一条指令for后面的大括号可以省略
for后面的三个参数都可以省略, 如果省略循环保持语句, 那么默认为真
Swift:
0.for后的圆括号可以省略
1.只能以bool作为条件语句
2.如果只有条指令for后面的大括号不可以省略
3.for后面的三个参数都可以省略, 如果省略循环保持语句, 那么默认为真
*/
// 2.0
//var sum:Int = 0
//for var i = 0; i <= 10 ; i++
//{
// i += 1
// sum = i
//}
//print(sum)
//var sum1:Int = 0
//var i1:Int = 0
//for ; i1 <= 10 ; i1++
//{
// i1 += 1
// sum1 = i1
//}
//print(sum1)
//var sum2:Int = 0
//var i2 = 0
//for ;i2 <= 10;
//{
// i2 += 1
// sum2 = i2
//}
//print(sum2)
//var sum3:Int = 0
//var i3 = 0
//for ; ;
//{
// i3 += 1
// sum3 = i3
// if i3 > 10
// {
// break
// }
//}
//print(sum3)
// 3.0 for in 代替
/*
for in循环
格式: for (接收参数 in 取出的参数) {需要执行的语句}
for in含义: 从(in)取出什么给什么, 直到取完为止
OC:
for (NSNumber *i in @[@1, @2, @3, @4, @5]) {
NSLog(@"%@", i);
}
NSDictionary *dict = @{@"name":@"lnj", @"age":@30};
for (NSArray *keys in dict.allKeys) {
NSLog(@"%@", keys);
}
NSDictionary *dict = @{@"name":@"lnj", @"age":@30};
for (NSArray *keys in dict.allValues) {
NSLog(@"%@", keys);
}
Swift:
for in 一般用于遍历区间或者集合
*/
var sum4:Int = 0
for i in 1..<10 // 会将区间的值一次赋值给i
{
sum4 += i
}
print(sum4)
for dict in ["name":"xiaohange","age":23] as [String : Any]
{
print(dict)
}
for (key, value) in ["name":"hjq", "age":24] as [String : Any]
{
print("key = (key) value = (value)")
}
//这样就完成了对数组的遍历了, 但是还有另一个情况, 如果我们想知道每次遍历的索引怎么办呢,还有一种方法:
let numberList = [1,2,3,4]
for num in numberList.enumerated(){
print("(num.offset) (num.element)")
}
for (index, item) in numberList.enumerated().reversed() {
print(index,item)
}
//区间(Range)循环
var rs = "";
for i in 0...10 {
rs += "(i)"
}
print(rs)
/* --- 2017.07.12 更新 */
/* 0 ~ 50 的遍历 跨步 10
此种方法相当于遍历开区间 0..<50, [0,50) 不会遍历最后一个数
用法常见对数组的遍历，可防止数组取值越界
*/
for i in stride(from: 0, to: 50, by: 10) {
print("i = (i)")
}
/* 0 ~ 20 的遍历 跨步 5
此种方法相当于遍历 0..<50 [0,50] 闭区间 会遍历最后一个数
*/
for j in stride(from: 0, through: 20, by: 5) {
print("j = (j)")
}
/*
遍历元组 (实际跟遍历字典类似)
*/
let tupleArray = [("zhangShang",60,170.0),
("liSi",77,175.0),
("wangWu",80,180.0)]
for t in tupleArray {
print("name : (t.0), weight : (t.1), height : (t.2)")
}