用法：

在要用到的类里倒入头文件（或者在pch里倒入也行），然后调用类方法即可。

cell.contentView.backgroundColor =[UIColor  colorWithHexString:@"#3579f4"];

.h文件：

@interface UIColor (UIcolor_RGB)

+ (UIColor*)colorWithHexString:(NSString*)stringToConvert;

@end

.m文件：

#import "UIColor+UIcolor_RGB.h"

@implementation UIColor (UIcolor_RGB)

+ (UIColor*)colorWithHexString:(NSString*)stringToConvert{

if([stringToConvert hasPrefix:@"#"])

{

stringToConvert = [stringToConvert substringFromIndex:1];

}

NSScanner*scanner = [NSScanner scannerWithString:stringToConvert];

unsigned hexNum;

if(![scanner scanHexInt:&hexNum])

{

return nil;

}

return[UIColor colorWithRGBHex:hexNum];

}

+ (UIColor*)colorWithRGBHex:(UInt32)hex{

int r = (hex >>16) &0xFF;

int g = (hex >>8) &0xFF;

int b = (hex) &0xFF;

return[UIColor colorWithRed:r /255.0f

green:g /255.0f

blue:b /255.0f

alpha:1.0f];

}

@end