1、数组

#import <Foundation/Foundation.h>

int arrays1[2];
int arrays2[] = {10,11};

int main(int argc, char *args[]) 
{
    @autoreleasepool
    {
        NSLog(@"%d", arrays1[1]); // int初始数据的值为0
        NSLog(@"%d", arrays2[1]); // 正常的存储

        int len3 = 3;
        NSString* arrays3[len3];
        NSLog(@"%@", arrays3[0]);

        char str2[] = {'I', ' ', 'L', 'o', 'v', 'e', ' ', 'y', 'o', 'u'};

        char charArr1[2] = "12";
        
        printf("====%s\n", charArr1);
    }
}

2、函数

#import <Foundation/Foundation.h>
#import "4_impFunc.h"

int main(int argc, char* args[]) 
{
    @autoreleasepool
    {
        NSLog(@"out count=%d", count);
        change();
        NSLog(@"out count=%d", count);

        printf("%d\n", add(1,2));
        printf("%d\n", add(3,4));
        printf("%d\n", add(5,6));
    }
}

3、引用

int add(int, int);
void change();
int count;

#import <Foundation/Foundation.h>

int count = 1;

int add(int a, int b)
{
    static int varAdd = 10;
    NSLog(@"change, varAdd=%d", varAdd);
    varAdd++;
    return a + b;
}

void change()
{
    NSLog(@"change, count=%d", count++);
}

4、define

#import <Foundation/Foundation.h>

#define PI 3.1415926
#define GIRTH(r) PI * 2 * (r)
#define AREA(r) PI * r * (r)

int main(int argc, char* args[])
{
    @autoreleasepool
    {
        NSLog(@"please input radius:");
        double radius;
        scanf("%lg", &radius);
        NSLog(@"图周长: %g", GIRTH(radius));
        NSLog(@"图面积: %g", AREA(radius));
    }
}

5、指针

#import <Foundation/Foundation.h>

int main(int argc, char* args[])
{
    @autoreleasepool
    {
        void swap(int*, int*);
        void copyStr(char*, char*);
        int maxNum(int*, int);
        int avgNum(int*, int);

        int a = 10;
        int b = 11;
        int* p1 = &a;
        int* p2 = &b;
        NSLog(@"before p1=%d, p2=%d", *p1, *p2);
        swap(p1, p2);
        NSLog(@"after p1=%d, p2=%d", *p1, *p2);

        int arr1[] = {1,2,3};
        for(int i = 0; i < sizeof(arr1) / sizeof(arr1[0]); i++)
        {
            NSLog(@"用最原始的办法遍历arr1 %d = %d", i, *(arr1 + i));
        }

        int arr2[] = {4,5,6,7};
        for(int* p = arr1, len = sizeof(arr1) / sizeof(arr1[0]); p < arr1 + len; p++)
        {
            NSLog(@"用指针的办法遍历arr1 %d", *p);
        }

        // 字符串复制
        char* str1 = "heheda";
        char str2[20];
        copyStr(str2, str1);
        NSLog(@"str2=%s", str2);

        // 指针调用函数
        int data[] = {1,3,2,9,8};
        int (*fnpt)();
        
        fnpt = maxNum;
        NSLog(@"maxValue = %d", (*fnpt)(data, 5));

        fnpt = avgNum;
        NSLog(@"maxValue = %d", (*fnpt)(data, 5));

    }
}

void swap(int* p1, int* p2)
{
    int tmp = *p2;
    *p2 = *p1;
    *p1 = tmp;
}

void copyStr(char* to, char* from)
{
    while(*from)
    {
        // NSLog(@"from=%c", *from);
        *to = *from;
        to++;
        from++;
    }
    *to = '\0';
}

int maxNum(int* dataArray, int len)
{
    int maxValue = *dataArray;
    for(int* p = dataArray; p < dataArray + len; p++)
    {
        if(*p > maxValue)
        {
            maxValue = *p;
        }
    }
    return maxValue;
}

int avgNum(int* dataArray, int len)
{
    int count = 0;
    for(int* p = dataArray; p < dataArray + len; p++)
    {
        count += *p;
    }
    return count / len;
}

7、结构体

#import <Foundation/Foundation.h>

int main(int argc, char* args[])
{
    @autoreleasepool
    {
        struct
        {
            int x;
            int y;
        } p1;
        struct POINT
        {
            int x1;
            int x2;
        };
        struct POINT p2;
        p1.x = 1;
        NSLog(@"p1.x = %d", p1.x);
        typedef struct POINT PPP;
        PPP p3;
        p3.x1 = 1001;
        NSLog(@"p3.x1=%d", p3.x1);
    }
}

8、block

#import <Foundation/Foundation.h>

typedef int (^Process)(int);
void processArray(int*, int, Process);

int main(int argc, char* args[])
{
    @autoreleasepool
    {
        void (^printStr)() = ^()
        {
            NSLog(@"this is printStr block");
        };
        printStr();

        double (^hybot)(double, double) =  ^ double (double num1, double num2)
        {
            return sqrt(num1 * num1 + num2 * num2);
        };
        NSLog(@"hybot=%f",hybot(1,2));

        // 不可修改
        int val1 = 10;
        void (^printMy)() = ^()
        {           
            NSLog(@"printMy val1 = %d", val1);
            int iValue111 = 11;
            NSLog(@"printMy iValue111 = %d", iValue111);

        };
        printMy();
        
        // 可以修改
        __block int val2 = 20;
        void (^printYou)() = ^()
        {
            NSLog(@"printYou val2 = %d", val2);
            val2 = 21;
            NSLog(@"printYou val2 = %d", val2);
        };
        val2 = 22;
        printYou();
        NSLog(@"printYou val2 = %d", val2);

        // 块作为函数参数. 我理解是抽象类的作法
        int array1[3] = {2,5,9};
        processArray(array1, 3, ^(int num)
        {
            return num * num;
        });
    }
}

void processArray(int* dataArray, int len, Process process)
{
    for(int* p = dataArray; p < dataArray + len; p++)
    {
        NSLog(@"result is %d", process(*p));
    }
}

9、hello world

#import <Foundation/Foundation.h>

int main(int argc, char *args[]) {
    @autoreleasepool {
        NSLog(@"Hello World my Object-C");

        long long b = 6440940218;
        NSLog(@"===%ld=====", (long) b);

        NSString *str1 = @"this is object-c string";
        NSLog(@"===%@===", str1);

        NSDate *date1 = [NSDate date];
        NSLog(@"====%@", date1);

        char char1 = 'a';
        char char2 = '\n';
        char char3 = 98;
        NSLog(@"==%d==%c==%c", char1, char2, char3);

        // 默认只保留6位小数. 需要时再指定
        double d1 = 12.345678901;
        NSLog(@"====%2.8f", d1);

        // 无穷大
        NSLog(@"====%g", 5 / 0.0);

        // 枚举， 本质就是无符号整型unsign int
        enum season {spring, summer, fall, winter};
        enum season s1 = spring;
        enum season s2 = summer;
        enum season s3 = fall;
        enum season s4 = winter;
        NSLog(@"====%u, %u, %u, %u", s1, s2, s3, s4);

        // BOOL在OC底层是unsign int, 只占1个字节. 所以给它大的话, 得到的结果不一定是YES
        BOOL b1 = 254;
        BOOL b2 = 1;
        NSLog(@"%d", b1 > b2);

        NSLog(@"===%d", (short) 33000);
        NSLog(@"===%d", (int) 32768);

    }
    return 0;
}