由于运行时需要，编译器用 char 字符串(char string) 形式对每个方法的返回值和参数进行编码，并且对 方法选择器(method selecor) 和该字符串进行关联。使用 @encode 获取类型的编码字符串， 使用 runtime 一些方法获取 method 的编码字符串
- (void)testTypeEncoding {
// char type encoding is:c
NSLog(@"char type encoding is:%s",@encode(char));
//int type encoding is:i
NSLog(@"int type encoding is:%s",@encode(int));
//short type encoding is:s
NSLog(@"short type encoding is:%s",@encode(short));
//long type encoding is:q
NSLog(@"long type encoding is:%s",@encode(long));
//long long type encoding is:q
NSLog(@"long long type encoding is:%s",@encode(long long));
//unsigned char type encoding is:C
NSLog(@"unsigned char type encoding is:%s",@encode(unsigned char));
//unsigned int type encoding is:I
NSLog(@"unsigned int type encoding is:%s",@encode(unsigned int));
//unsigned short type encoding is:S
NSLog(@"unsigned short type encoding is:%s",@encode(unsigned short));
//unsigned long type encoding is:Q
NSLog(@"unsigned long type encoding is:%s",@encode(unsigned long));
//unsigned long long type encoding is:Q
NSLog(@"unsigned long long type encoding is:%s",@encode(unsigned long long));
//float type encoding is:f
NSLog(@"float type encoding is:%s",@encode(float));
//double type encoding is:d
NSLog(@"double type encoding is:%s",@encode(double));
//bool type encoding is:B
NSLog(@"bool type encoding is:%s",@encode(bool));
//void type encoding is:v
NSLog(@"void type encoding is:%s",@encode(void));
//id type encoding is:@
NSLog(@"id type encoding is:%s",@encode(id));
//class type encoding is:#
NSLog(@"class type encoding is:%s",@encode(Class));
//SEL type encoding is :
NSLog(@"SEL type encoding is %s",@encode(SEL));
//IMP type encoding is:^?
NSLog(@"IMP type encoding is:%s",@encode(IMP));
//Method type encoding is:^{objc_method=}
NSLog(@"Method type encoding is:%s",@encode(Method));
//Array type encoding is:{NSArray=#}
NSLog(@"Array type encoding is:%s",@encode(NSArray));
typedef struct Person_S {
char *name;
float age;
} Person_S;
//structure type encoding is:{Person_S=*f}
NSLog(@"structure type encoding is:%s",@encode(Person_S));
typedef union {
double d;
// uint32_t u32[2];
} U;
NSLog(@"union type encoding is:%s",@encode(U)); //why
// 指针的标准编码是加一个前置的 ^，而 char * 拥有自己的编码 *。
// 这在概念上是很好理解的，因为 C 的字符串被认为是一个实体，而不是指针。
//char * type encoding is:*
NSLog(@"char * type encoding is:%s",@encode(char *));
//float * type encoding is:^f
NSLog(@"float * type encoding is:%s",@encode(float *));
int a = 2;
int *b = {&a};
// int[] --> ^i
NSLog(@"int[] --> %s",@encode(typeof(b)));
typedef struct {
unsigned int widthValidated : 3;
unsigned int heightValidated : 3;
} status2;
//bit num type encoding is:{?=b3b3}
NSLog(@"bit num type encoding is:%s",@encode(status2));
}
有了上面的内容，可以实现判断 NSNumber 中存放内容的实际类型 from: https://blog.csdn.net/yhawaii/article/details/8222973
- (void)testNumEncoding {
NSDictionary *dic = [NSDictionary dictionaryWithObjectsAndKeys:
[NSNumber numberWithBool:YES],@"key1",
[NSNumber numberWithDouble:1.00f],@"key2",
[NSNumber numberWithInt:1],@"key3",
[NSNumber numberWithFloat:33.0f], @"key4", nil];
for(NSString *key in dic){
id value = [dic valueForKey:key];
if([value isKindOfClass:[NSNumber class]]){
const char * pObjCType = [((NSNumber*)value) objCType];
if (strcmp(pObjCType, @encode(int)) == 0) {
NSLog(@"字典中key=%@的值是int类型,值为%d",key,[value intValue]);
}
if (strcmp(pObjCType, @encode(float)) == 0) {
NSLog(@"字典中key=%@的值是float类型,值为%f",key,[value floatValue]);
}
if (strcmp(pObjCType, @encode(double)) == 0) {
NSLog(@"字典中key=%@的值是double类型,值为%f",key,[value doubleValue]);
}
if (strcmp(pObjCType, @encode(BOOL)) == 0) {
NSLog(@"字典中key=%@的值是bool类型,值为%i",key,[value boolValue]);
}
}
}
}参考