循环结构

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

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++
i2++
}
print(sum2)


var sum3:Int = 0
var i3 = 0
for ; ;
{
sum3 = i3++
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":@"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 i4 in 1...10 // 会将区间的值依次赋值给i
{
sum4 += i4;
}
print(sum4)

for dict in ["name":"lnj", "age":30]
{
print(dict);
}

for (key, value) in ["name":"lnj", "age":30]
{
print("\(key) = \(value)")
}

while循环

格式:while(循环保持条件){需要执行的语句}
OC:
int i = 0;
int sum = 0;
while (i <= 10) {
sum = i++;
}

while (i <= 10)
sum = i++;

NSLog(@"%d", sum);
如果只有一条指令while后面的大括号可以省略

Swift:
0.while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while后面的大括号不可以省略

var i:Int = 0
var sum:Int = 0
while (i <= 10)
{
sum = i++
}
print("\(sum)")

var i1:Int = 0
var sum1:Int = 0
while i1 <= 10
{
sum1 = i1++
}
print("\(sum1)")

do while循环

格式:do while(循环保持条件) {需要执行的语句}
OC:
int i = 0;
int sum = 0;
do {
sum = i++;
} while (i <= 10);
NSLog(@"%d", sum);

int i = 0;
int sum = 0;
do
sum = i++;
while (i <= 10);
NSLog(@"%d", sum);
如果只有一条指令do后面的大括号可以省略

Swift2.0之后变为 repeat while, do用于捕捉异常
0.while后的圆括号可以省略
1.只能以bool作为条件语句
2.如果只有一条指令repeat后面的大括号不可以省略

var i2:Int = 0
var sum2:Int = 0
repeat{
sum2 = i2++;
}while(i2 <= 10)
print(sum2)

var i3:Int = 0
var sum3:Int = 0
repeat{
sum3 = i3++;
}while i3 <= 10
print(sum3)