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++;
}
NSLog(@"%d", sum);
int sum = 0;
int i = 0;
for ( ; ; ) {
sum = i++;
if (i > 10) {
break;
}
}
NSLog(@"%d", sum);
int sum = 0;
int i = 0;
for ( ; ; ) {
sum = 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1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
var sum:Int = 0
for var i = 0 ; i <= 10 ; i++
{
sum = i++
}
print(sum)
var sum1:Int = 0
var i1 = 0
for ; i1 <= 10 ; i1++
{
sum1 = i1++
}
print(sum1)
var sum2:Int = 0
var i2 = 0
for ; i2 <= 10;
{
sum2 = i2++
}
print(sum2)
var sum3:Int = 0
var i3 = 0
for ; ;
{
sum3 = i3++
if i3 > 10
{
break
}
}
print(sum3)
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":@"solozyx", @"age":@99};
for (NSArray *keys in dict.allKeys) {
NSLog(@"%@", keys);
}
NSDictionary *dict = @{@"name":@"solozyx", @"age":@99};
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 i4 in 1...10 // 会将区间的值依次赋值给i
{
sum4 += i4;
}
print(sum4)
for dict in ["name":"solozyx", "age":99]
{
print(dict);
}
for (key, value) in ["name":"solozyx", "age":99]
{
print("\(key) = \(value)")
}
