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动态映射objective-c的对象方法修改空指针
2014-08-14 11:11:13         来源:likandmydeer的专栏  
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背景:目前iOS工程较多将json数据转换成一个对象来储存。假设这个对象有一个Attributes为NSString类型叫myName,这个Attributes一直是nil,创建这对象后忘记对它赋值。现在要通过一个函数来检测他出来,再将他赋值为@“”;


另外,我不知道有多少个Attributes,只要是NSString类型而且Attributes是nil就赋值为@“”。


代码如下:

//

// GMCommonHelper.h

#import

#import



@interface GMCommonHelper : NSObject


+(void)fixNilData:(id)kClass;


@end


//

// GMCommonHelper.m

#import


#import “GMCommonHelper.h"

@implementation GMCommonHelper


+(void)fixNilData:(id)kClass

{

unsigned int propertyCount = 0;

objc_property_t *properties = class_copyPropertyList([kClass class], &propertyCount);

for (unsigned int i = 0; i < propertyCount; ++i) {

objc_property_t property = properties[i];

const char * name = property_getName(property);

const char * attrs = property_getAttributes(property);

NSString * utf8Name = [NSString stringWithUTF8String:name];

NSString * utf8Attrs = [NSString stringWithUTF8String:attrs];

id propertVal = [kClass valueForKey:utf8Name];

if (!propertVal && [utf8Attrs hasPrefix:@"T@\"NSString\""]) {

[kClass setValue:@"" forKey:utf8Name];

}

}

free(properties);

}



//———————————————————————


- (void)releaseProperties { unsigned int c = 0; objc_property_t *properties = class_copyPropertyList([self class], &c); for(unsigned int i = 0; i < c; i++) { objc_property_t property = properties[i]; NSString *propertyName = [NSString stringWithUTF8String:property_getName(property)]; NSString *propertyType = [NSString stringWithUTF8String:property_getAttributes(property)]; if([propertyType hasPrefix:@"T@"] // is an object && [propertyType rangeOfString:@",R,"].location == NSNotFound // not readonly ) { [self setValue:nil forKey:propertyName]; NSLog(@"%@.%@ = %@", NSStringFromClass(cls), propertyName, [self valueForKey:propertyName]); } } free(properties);}

//———————————————————————



If you only care about classes you can use isKindOfClass:, but if you want to deal with scalars you are correct that you need to use property_getAttributes(), it returns a string that encodes the type information. Below is a basic function that demonstrates what you need to do. For examples of encoding strings, look here.

unsigned int outCount, i;
objc_property_t *properties = class_copyPropertyList([object class], &outCount);
for (i = 0; i < outCount; i++) {
    objc_property_t property = properties[i];
    char *property_name = property_getName(property);
    char *property_type = property_getAttributes(property);

    switch(property_type[1]) {
      case 'f' : //float
        break;
      case 's' : //short
        break;
      case '@' : //ObjC object
        //Handle different clases in here
        break;
    }
}

Obvviously you will need to add all the types and classes you need to handle to this, it uses the normal ObjC @encode type。

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