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#import "ViewController.h"
#import "Student.h"
#import "Course.h"
@interface ViewController ()
@end
@implementation ViewController
- (void)viewDidLoad {
[super viewDidLoad];
[self useKey];
[self useKeyPath];
[self performCollection];
[self performDictionary];
}
* .m文件也没有实现。name属性没有加property，原来的访问方法就访问不了name属性了。
使用KVC就可以轻松实现
*/
- (void)useKey {
Student *student = [[Student alloc] init];
[student setValue:@"Benjamin" forKey:@"name"];
NSString *name = [student valueForKey:@"name"];
NSLog(@"学生姓名：%@", name);
NSLog(@"------------------------------------");
}
* 使用Keypath(键路径)访问属性
*/
- (void)useKeyPath {
Student *student = [[Student alloc] init];
[student setValue:@"Benjamin" forKey:@"name"];
Course *course = [[Course alloc] init];
[course setValue:@"语文课" forKey:@"courseName"];
[student setValue:course forKey:@"course"];
NSString *courseName = [student valueForKeyPath:@"course.courseName"];
NSLog(@"课程名称：%@", courseName);
[student setValue:@"数学课" forKeyPath:@"course.courseName"];
courseName = [student valueForKeyPath:@"course.courseName"];
NSLog(@"新课程名称：%@", courseName);
[student setValue:@"88" forKey:@"point"];
NSString *point = [student valueForKey:@"point"];
NSLog(@"point: %@", point);
[student setValue:[NSNumber numberWithInteger:88] forKey:@"point"];
NSNumber *newPoint = [student valueForKey:@"point"];
NSLog(@"newPoint: %@", newPoint);
NSLog(@"------------------------------------");
}
* 操作集合
可以使用集合操作计算学生的平均分、最高分、总分、总人数等数据
*/
- (void)performCollection {
Student *student = [[Student alloc]init];
[student setValue:@"张三" forKey:@"name"];
Student *s1 = [[Student alloc] init];
Student *s2 = [[Student alloc] init];
Student *s3 = [[Student alloc] init];
[s1 setValue:@"77" forKey:@"point"];
[s2 setValue:@"88" forKey:@"point"];
[s3 setValue:@"99" forKey:@"point"];
NSArray *studentArray = [NSArray arrayWithObjects:s1, s2, s3, nil];
[student setValue:studentArray forKey:@"otherStudent"];
NSLog(@"其他学生的成绩: %@", [student valueForKeyPath: @"otherStudent.point"]);
NSLog(@"共有%@个学生", [student valueForKeyPath: @"otherStudent.@count"]);
NSLog(@"学生的总分: %@", [student valueForKeyPath: @"otherStudent.@sum.point"]);
NSLog(@"学生的最高分: %@", [student valueForKeyPath: @"otherStudent.@max.point"]);
NSLog(@"学生的最低分: %@", [student valueForKeyPath: @"otherStudent.@min.point"]);
NSLog(@"平均成绩: %@", [student valueForKeyPath: @"otherStudent.@avg.point"]);
输出结果
2016-01-04 12:05:46.528 testOC[29855:945179] 其他学生的成绩: (
77,
88,
99
)
2016-01-04 12:05:46.529 testOC[29855:945179] 共有3个学生
2016-01-04 12:05:46.529 testOC[29855:945179] 学生的总分: 264
2016-01-04 12:05:46.529 testOC[29855:945179] 学生的最高分: 99
2016-01-04 12:05:46.529 testOC[29855:945179] 学生的最低分: 77
2016-01-04 12:05:46.529 testOC[29855:945179] 平均成绩: 88
**/
NSLog(@"------------------------------------");
}
* 操作字典
*/
- (void)performDictionary {
NSDictionary *dic = @{@"name": @"jack",
@"point": [NSNumber numberWithInteger:12]};
Student *student = [[Student alloc] init];
[student setValuesForKeysWithDictionary:dic];
NSLog(@"姓名为: %@, 分数为: %@", [student valueForKey: @"name"], [student valueForKey: @"point"]);
结果为
姓名为: jack, 分数为: 12
**/
NSLog(@"------------------------------------");
}
实际使用举例
利用kvc的这个特性，我们可以访问系统里的一些私有变量。
例如：在UIPageControl里面有两个私有变量：
UIImage *_currentPageImage;
UIImage *_pageImage;
* 设置pageControl当前显示和未显示到脚标的样式了
*/
- (void)changePageControlImage {
UIPageControl *pageControl = [[UIPageControl alloc] init];
[pageControl setValue:[UIImage imageNamed:@"XX"] forKey:@"_currentPageImage"];
[pageControl setValue:[UIImage imageNamed:@"YY"] forKey:@"_pageImage"];
UIImage *currentImage = [pageControl valueForKey:@"_currentPageImage"];
UIImage *pageImage = [pageControl valueForKey:@"_pageImage"];
NSLog(@"currentImage: %@, pageImage: %@", currentImage, pageImage);
NSLog(@"------------------------------------");
}
@end
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