KVC底层实现的是setter和getter方法。
KVC简介
代码准备
苹果官方文档查阅
//类LGPerson中的方法
#import "LGStudent.h"
NS_ASSUME_NONNULL_BEGIN
typedef struct {
float x, y, z;
} ThreeFloats;
@interface LGPerson : NSObject{
@public
NSString *myName;
}
@property (nonatomic, copy) NSString *name;
@property (nonatomic, strong) NSArray *array;
@property (nonatomic, strong) NSMutableArray *mArray;
@property (nonatomic, assign) int age;
@property (nonatomic) ThreeFloats threeFloats;
@property (nonatomic, strong) LGStudent *student;
@end
//类LGStudent中的方法
@interface LGStudent : NSObject
@property (nonatomic, copy) NSString *name;
@property (nonatomic, copy) NSString *subject;
@property (nonatomic, copy) NSString *nick;
@property (nonatomic, assign) int age;
@property (nonatomic, assign) int length;
@property (nonatomic, strong) NSMutableArray *penArr;
@end
KVC设置的过程底层的代码是objc_setProperty_noatomic_copy(这个copy不一定，根据参数类型来定的)->reallySetProperty(self,_cmd,newValue,offSet,false,true,false)等方法。
（可以使用VSCode编译器，查看下源码）
LGPerson *person = [[LGPerson alloc] init];
// 一般setter 方法
person.name = @"LG_Cooci";
person.age = 18;
person->myName = @"cooci";
NSLog(@"%@ - %d - %@",person.name,person.age,person->myName);
// 1:Key-Value Coding (KVC) : 基本类型
[person setValue:@"KC" forKey:@"name"];
[person setValue:@19 forKey:@"age"];
[person setValue:@"酷C" forKey:@"myName"];
NSLog(@"%@ - %@ - %@",[person valueForKey:@"name"],[person valueForKey:@"age"],[person valueForKey:@"myName"]);
// 2:KVC - 集合类型 -
person.array = @[@"1",@"2",@"3"];
// 由于不是可变数组 - 无法做到
// person.array[0] = @"100";
NSArray *array = [person valueForKey:@"array"];
// 用 array 的值创建一个新的数组
array = @[@"100",@"2",@"3"];
[person setValue:array forKey:@"array"];
NSLog(@"%@",[person valueForKey:@"array"]);
// KVC 的方式
NSMutableArray *ma = [person mutableArrayValueForKey:@"array"];
ma[0] = @"100";
NSLog(@"%@",[person valueForKey:@"array"]);
// 3:KVC - 集合操作符
//[self dictionaryTest];
//[self arrayMessagePass];
//[self aggregationOperator];
//[self arrayOperator];
//[self arrayNesting];
//[self setNesting];
//[self arrayDemo];
// 4:KVC - 访问非对象属性
ThreeFloats floats = {1., 2., 3.};
NSValue *value = [NSValue valueWithBytes:&floats objCType:@encode(ThreeFloats)];
[person setValue:value forKey:@"threeFloats"];
NSValue *reslut = [person valueForKey:@"threeFloats"];
NSLog(@"%@",reslut);
ThreeFloats th;
[reslut getValue:&th] ;
NSLog(@"%f - %f - %f",th.x,th.y,th.z);
// 5:KVC - 层层访问
LGStudent *student = [[LGStudent alloc] init];
student.subject = @"iOS";
person.student = student;
[person setValue:@"大师班" forKeyPath:@"student.subject"];
NSLog(@"%@",[person valueForKeyPath:@"student.subject"]);
}
#pragma mark - array取值
- (void)arrayDemo{
LGStudent *p = [LGStudent new];
p.penArr = [NSMutableArray arrayWithObjects:@"pen0", @"pen1", @"pen2", @"pen3", nil];
NSArray *arr = [p valueForKey:@"pens"]; // 动态成员变量
NSLog(@"pens = %@", arr);
//NSLog(@"%@",arr[0]);
NSLog(@"%d",[arr containsObject:@"pen9"]);
// 遍历
NSEnumerator *enumerator = [arr objectEnumerator];
NSString* str = nil;
while (str = [enumerator nextObject]) {
NSLog(@"%@", str);
}
}
#pragma mark - 字典操作
- (void)dictionaryTest{
NSDictionary* dict = @{
@"name":@"Cooci",
@"nick":@"KC",
@"subject":@"iOS",
@"age":@18,
@"length":@180
};
LGStudent *p = [[LGStudent alloc] init];
// 字典转模型
[p setValuesForKeysWithDictionary:dict];
NSLog(@"%@",p);
// 键数组转模型到字典
NSArray *array = @[@"name",@"age"];
NSDictionary *dic = [p dictionaryWithValuesForKeys:array];
NSLog(@"%@",dic);
}
#pragma mark - KVC消息传递
- (void)arrayMessagePass{
NSArray *array = @[@"Hank",@"Cooci",@"Kody",@"CC"];
NSArray *lenStr= [array valueForKeyPath:@"length"];
NSLog(@"%@",lenStr);// 消息从array传递给了string
NSArray *lowStr= [array valueForKeyPath:@"lowercaseString"];
NSLog(@"%@",lowStr);
}
#pragma mark - 聚合操作符
// @avg、@count、@max、@min、@sum
- (void)aggregationOperator{
NSMutableArray *personArray = [NSMutableArray array];
for (int i = 0; i < 6; i++) {
LGStudent *p = [LGStudent new];
NSDictionary* dict = @{
@"name":@"Tom",
@"age":@(18+i),
@"nick":@"Cat",
@"length":@(175 + 2*arc4random_uniform(6)),
};
[p setValuesForKeysWithDictionary:dict];
[personArray addObject:p];
}
NSLog(@"%@", [personArray valueForKey:@"length"]);
/// 平均身高
float avg = [[personArray valueForKeyPath:@"@avg.length"] floatValue];
NSLog(@"%f", avg);
int count = [[personArray valueForKeyPath:@"@count.length"] intValue];
NSLog(@"%d", count);
int sum = [[personArray valueForKeyPath:@"@sum.length"] intValue];
NSLog(@"%d", sum);
int max = [[personArray valueForKeyPath:@"@max.length"] intValue];
NSLog(@"%d", max);
int min = [[personArray valueForKeyPath:@"@min.length"] intValue];
NSLog(@"%d", min);
}
// 数组操作符 @distinctUnionOfObjects @unionOfObjects
- (void)arrayOperator{
NSMutableArray *personArray = [NSMutableArray array];
for (int i = 0; i < 6; i++) {
LGStudent *p = [LGStudent new];
NSDictionary* dict = @{
@"name":@"Tom",
@"age":@(18+i),
@"nick":@"Cat",
@"length":@(175 + 2*arc4random_uniform(6)),
};
[p setValuesForKeysWithDictionary:dict];
[personArray addObject:p];
}
NSLog(@"%@", [personArray valueForKey:@"length"]);
// 返回操作对象指定属性的集合
NSArray* arr1 = [personArray valueForKeyPath:@"@unionOfObjects.length"];
NSLog(@"arr1 = %@", arr1);
// 返回操作对象指定属性的集合 -- 去重
NSArray* arr2 = [personArray valueForKeyPath:@"@distinctUnionOfObjects.length"];
NSLog(@"arr2 = %@", arr2);
}
// 嵌套集合(array&set)操作 @distinctUnionOfArrays @unionOfArrays @distinctUnionOfSets
- (void)arrayNesting{
NSMutableArray *personArray1 = [NSMutableArray array];
for (int i = 0; i < 6; i++) {
LGStudent *student = [LGStudent new];
NSDictionary* dict = @{
@"name":@"Tom",
@"age":@(18+i),
@"nick":@"Cat",
@"length":@(175 + 2*arc4random_uniform(6)),
};
[student setValuesForKeysWithDictionary:dict];
[personArray1 addObject:student];
}
NSMutableArray *personArray2 = [NSMutableArray array];
for (int i = 0; i < 6; i++) {
LGPerson *person = [LGPerson new];
NSDictionary* dict = @{
@"name":@"Tom",
@"age":@(18+i),
@"nick":@"Cat",
@"length":@(175 + 2*arc4random_uniform(6)),
};
[person setValuesForKeysWithDictionary:dict];
[personArray2 addObject:person];
}
// 嵌套数组
NSArray* nestArr = @[personArray1, personArray2];
NSArray* arr = [nestArr valueForKeyPath:@"@distinctUnionOfArrays.length"];
NSLog(@"arr = %@", arr);
NSArray* arr1 = [nestArr valueForKeyPath:@"@unionOfArrays.length"];
NSLog(@"arr1 = %@", arr1);
}
- (void)setNesting{
NSMutableSet *personSet1 = [NSMutableSet set];
for (int i = 0; i < 6; i++) {
LGStudent *person = [LGStudent new];
NSDictionary* dict = @{
@"name":@"Tom",
@"age":@(18+i),
@"nick":@"Cat",
@"length":@(175 + 2*arc4random_uniform(6)),
};
[person setValuesForKeysWithDictionary:dict];
[personSet1 addObject:person];
}
NSLog(@"personSet1 = %@", [personSet1 valueForKey:@"length"]);
NSMutableSet *personSet2 = [NSMutableSet set];
for (int i = 0; i < 6; i++) {
LGPerson *person = [LGPerson new];
NSDictionary* dict = @{
@"name":@"Tom",
@"age":@(18+i),
@"nick":@"Cat",
@"length":@(175 + 2*arc4random_uniform(6)),
};
[person setValuesForKeysWithDictionary:dict];
[personSet2 addObject:person];
}
NSLog(@"personSet2 = %@", [personSet2 valueForKey:@"length"]);
// 嵌套set
NSSet* nestSet = [NSSet setWithObjects:personSet1, personSet2, nil];
// 交集
NSArray* arr1 = [nestSet valueForKeyPath:@"@distinctUnionOfSets.length"];
NSLog(@"arr1 = %@", arr1);
}
KVC取值&赋值过程
pragma mark - 关闭或开启实例变量赋值
- (BOOL)accessInstanceVariablesDirectly{
默认返回为YES，如果返回为NO，则报错（setValue:forUndefinedKey:）。
return YES;
}
setvalue:forkey(是成员变量分析而不是属性分析)
属性系统自动为我们实现了set和get方法了。
LGPerson *person = [[LGPerson alloc] init];
// 1: KVC - 设置值的过程 _,_is,,is的过程
// [person setValue:@"LG_Cooci" forKey:@"name"];
// NSLog(@"%@-%@-%@-%@",person->_name,person->_isName,person->name,person->isName);
// NSLog(@"%@-%@-%@",person->_isName,person->name,person->isName);
// NSLog(@"%@-%@",person->name,person->isName);
// NSLog(@"%@",person->isName);
// 2: KVC - 取值的过程
// person->_name = @"_name";
// person->_isName = @"_isName";
// person->name = @"name";
// person->isName = @"isName";
// NSLog(@"取值:%@",[person valueForKey:@"name"]);
//MARK: - valueForKey 流程分析 - get
accessor method is an NSNumber scalar type or NSValue structure type but the value is nil,
只针对NSValue以及NSNumber的
- (void)setNilValueForKey:(NSString *)key;
自定义KVC
#import
@implementation NSObject (LGKVC)
- (void)lg_setValue:(nullable id)value forKey:(NSString *)key{
// 1:非空判断一下
if (key == nil || key.length == 0) return;
// 2:找到相关方法 set _set setIs
// key 要大写
NSString *Key = key.capitalizedString;
// 拼接方法
NSString *setKey = [NSString stringWithFormat:@"set%@:",Key];
NSString *_setKey = [NSString stringWithFormat:@"_set%@:",Key];
NSString *setIsKey = [NSString stringWithFormat:@"setIs%@:",Key];
if ([self lg_performSelectorWithMethodName:setKey value:value]) {
NSLog(@"*********%@**********",setKey);
return;
}else if ([self lg_performSelectorWithMethodName:_setKey value:value]) {
NSLog(@"*********%@**********",_setKey);
return;
}else if ([self lg_performSelectorWithMethodName:setIsKey value:value]) {
NSLog(@"*********%@**********",setIsKey);
return;
}
// 3:判断是否能够直接赋值实例变量
if (![self.class accessInstanceVariablesDirectly] ) {
@throw [NSException exceptionWithName:@"LGUnknownKeyException" reason:[NSString stringWithFormat:@"****[%@ valueForUndefinedKey:]: this class is not key value coding-compliant for the key name.****",self] userInfo:nil];
}
// 4.找相关实例变量进行赋值
// 4.1 定义一个收集实例变量的可变数组
NSMutableArray *mArray = [self getIvarListName];
// _ _is is
NSString *_key = [NSString stringWithFormat:@"_%@",key];
NSString *_isKey = [NSString stringWithFormat:@"_is%@",Key];
NSString *isKey = [NSString stringWithFormat:@"is%@",Key];
if ([mArray containsObject:_key]) {
// 4.2 获取相应的 ivar
Ivar ivar = class_getInstanceVariable([self class], _key.UTF8String);
// 4.3 对相应的 ivar 设置值
object_setIvar(self , ivar, value);
return;
}else if ([mArray containsObject:_isKey]) {
Ivar ivar = class_getInstanceVariable([self class], _isKey.UTF8String);
object_setIvar(self , ivar, value);
return;
}else if ([mArray containsObject:key]) {
Ivar ivar = class_getInstanceVariable([self class], key.UTF8String);
object_setIvar(self , ivar, value);
return;
}else if ([mArray containsObject:isKey]) {
Ivar ivar = class_getInstanceVariable([self class], isKey.UTF8String);
object_setIvar(self , ivar, value);
return;
}
// 5:如果找不到相关实例
@throw [NSException exceptionWithName:@"LGUnknownKeyException" reason:[NSString stringWithFormat:@"****[%@ %@]: this class is not key value coding-compliant for the key name.****",self,NSStringFromSelector(_cmd)] userInfo:nil];
}
- (nullable id)lg_valueForKey:(NSString *)key{
// 1:刷选key 判断非空
if (key == nil || key.length == 0) {
return nil;
}
// 2:找到相关方法 get countOf objectInAtIndex
// key 要大写
NSString *Key = key.capitalizedString;
// 拼接方法
NSString *getKey = [NSString stringWithFormat:@"get%@",Key];
NSString *countOfKey = [NSString stringWithFormat:@"countOf%@",Key];
NSString *objectInKeyAtIndex = [NSString stringWithFormat:@"objectIn%@AtIndex:",Key];
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Warc-performSelector-leaks"
if ([self respondsToSelector:NSSelectorFromString(getKey)]) {
return [self performSelector:NSSelectorFromString(getKey)];
}else if ([self respondsToSelector:NSSelectorFromString(key)]){
return [self performSelector:NSSelectorFromString(key)];
}else if ([self respondsToSelector:NSSelectorFromString(countOfKey)]){
if ([self respondsToSelector:NSSelectorFromString(objectInKeyAtIndex)]) {
int num = (int)[self performSelector:NSSelectorFromString(countOfKey)];
NSMutableArray *mArray = [NSMutableArray arrayWithCapacity:1];
for (int i = 0; i _is is
// _name -> _isName -> name -> isName
NSString *_key = [NSString stringWithFormat:@"_%@",key];
NSString *_isKey = [NSString stringWithFormat:@"_is%@",Key];
NSString *isKey = [NSString stringWithFormat:@"is%@",Key];
if ([mArray containsObject:_key]) {
Ivar ivar = class_getInstanceVariable([self class], _key.UTF8String);
return object_getIvar(self, ivar);;
}else if ([mArray containsObject:_isKey]) {
Ivar ivar = class_getInstanceVariable([self class], _isKey.UTF8String);
return object_getIvar(self, ivar);;
}else if ([mArray containsObject:key]) {
Ivar ivar = class_getInstanceVariable([self class], key.UTF8String);
return object_getIvar(self, ivar);;
}else if ([mArray containsObject:isKey]) {
Ivar ivar = class_getInstanceVariable([self class], isKey.UTF8String);
return object_getIvar(self, ivar);;
}
return @"";
}
#pragma mark - 相关方法
- (BOOL)lg_performSelectorWithMethodName:(NSString *)methodName value:(id)value{
if ([self respondsToSelector:NSSelectorFromString(methodName)]) {
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Warc-performSelector-leaks"
[self performSelector:NSSelectorFromString(methodName) withObject:value];
#pragma clang diagnostic pop
return YES;
}
return NO;
}
- (id)performSelectorWithMethodName:(NSString *)methodName{
if ([self respondsToSelector:NSSelectorFromString(methodName)]) {
#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Warc-performSelector-leaks"
return [self performSelector:NSSelectorFromString(methodName) ];
#pragma clang diagnostic pop
}
return nil;
}
- (NSMutableArray *)getIvarListName{
NSMutableArray *mArray = [NSMutableArray arrayWithCapacity:1];
unsigned int count = 0;
Ivar *ivars = class_copyIvarList([self class], &count);
for (int i = 0; i KVC异常处理技巧
LGPerson *person = [[LGPerson alloc] init];
// 1: KVC 自动转换类型
NSLog(@"******1: KVC - int -> NSNumber - 结构体******");
[person setValue:@18 forKey:@"age"];
// 上面那个表达 大家应该都会! 但是下面这样操作可以?
[person setValue:@"20" forKey:@"age"]; // int - string
NSLog(@"%@-%@",[person valueForKey:@"age"],[[person valueForKey:@"age"] class]);//__NSCFNumber
[person setValue:@"20" forKey:@"sex"];
NSLog(@"%@-%@",[person valueForKey:@"sex"],[[person valueForKey:@"sex"] class]);//__NSCFNumber
ThreeFloats floats = {1., 2., 3.};
NSValue *value = [NSValue valueWithBytes:&floats objCType:@encode(ThreeFloats)];
[person setValue:value forKey:@"threeFloats"];
NSLog(@"%@-%@",[person valueForKey:@"threeFloats"],[[person valueForKey:@"threeFloats"] class]);//NSConcreteValue
// 2: 设置空值
NSLog(@"******2: 设置空值******");
[person setValue:nil forKey:@"age"]; // subject不会走 - 官方注释里面说只对 NSNumber - NSValue
[person setValue:nil forKey:@"subject"];
// 3: 找不到的 key
NSLog(@"******3: 找不到的 key******");
[person setValue:nil forKey:@"KC"];
// 4: 取值时 - 找不到 key
NSLog(@"******4: 取值时 - 找不到 key******");
NSLog(@"%@",[person valueForKey:@"KC"]);
// 5: 键值验证
NSLog(@"******5: 键值验证******");
NSError *error;
NSString *name = @"LG_Cooci";
if (![person validateValue:&name forKey:@"names" error:&error]) {
NSLog(@"%@",error);
}else{
NSLog(@"%@",[person valueForKey:@"name"]);
}
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