iOS开发随笔（一）---记录开发中的小方法

1.判断字符串为空和只为空格解决办法

+ (BOOL)isBlankString:(NSString *)string
{
    if  (string == nil)  {

        return YES;

    }
    
    if (string == NULL) {
        
        return YES;
        
    }
    
    if ([string isKindOfClass:[NSNull class]]) {
        
        return YES;
        
    }
    
    if ([[string stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]] length]==0) {
        
        return YES;
        
    }
    if ([[string stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]] isEqualToString:@"null"]||[[string stringByTrimmingCharactersInSet:[NSCharacterSet whitespaceAndNewlineCharacterSet]] isEqualToString:@"(null)"]) {
        
        return YES;
        
    }
    return NO;
    
}

2.限制textfiled 文字字数（textview同理）

+ (void)limitTextField:(UITextField *)textField limitNum:(NSUInteger)num
{
    /**
     *  最大输入长度,中英文字符都按一个字符计算
     */
    UITextField *textfield = textField;
    NSString *toBeString = textfield.text;
    // 获取键盘输入模式

    NSString *lang = textfield.textInputMode.primaryLanguage;

    // 中文输入的时候,可能有markedText(高亮选择的文字),需要判断这种状态

    // zh-Hans表示简体中文输入, 包括简体拼音，健体五笔，简体手写

    if ([lang isEqualToString:@"zh-Hans"]) {

        UITextRange *selectedRange = [textfield markedTextRange];
        //获取高亮选择部分
        UITextPosition *position = [textfield positionFromPosition:selectedRange.start offset:0];
        // 没有高亮选择的字，表明输入结束,则对已输入的文字进行字数统计和限制
        if (!position) {
            if (toBeString.length > num) {
                // 截取子串
                textfield.text = [toBeString substringToIndex:num];
            }
        }
    } else {
        // 中文输入法以外的直接对其统计限制即可，不考虑其他语种情况
        if (toBeString.length > num) {
            // 截取子串
            textfield.text = [toBeString substringToIndex:num];
        }

    }
}

3.判断时间 1过期 0相等 -1没过期

+(int)compareOneDay:(NSDate *)oneDay withAnotherDay:(NSDate *)anotherDay
{
    NSDateFormatter *dateFormatter = [[NSDateFormatter alloc] init];
    [dateFormatter setDateFormat:@"yyyy-MM-dd hh:mm:ss"];
    NSString *oneDayStr = [dateFormatter stringFromDate:oneDay];
    NSString *anotherDayStr = [dateFormatter stringFromDate:anotherDay];
    NSDate *dateA = [dateFormatter dateFromString:oneDayStr];
    NSDate *dateB = [dateFormatter dateFromString:anotherDayStr];
    NSComparisonResult result = [dateA compare:dateB];
    NSLog(@"oneDay : %@, anotherDay : %@", oneDay, anotherDay);
    if (result == NSOrderedDescending) {
        //在指定时间前面 过了指定时间 过期
        NSLog(@"oneDay  is in the future");
        return 1;
    }
    else if (result == NSOrderedAscending){
        //没过指定时间 没过期
        //NSLog(@"Date1 is in the past");
        return -1;
    }
    //刚好时间一样.
    //NSLog(@"Both dates are the same");
    return 0;

}

5.相机获取到的图片自动旋转90度解决办法

+ (UIImage *)fixOrientation:(UIImage *)aImage {

    if (aImage.imageOrientation == UIImageOrientationUp)
        
        return aImage;
    
    CGAffineTransform transform = CGAffineTransformIdentity;
    
    switch (aImage.imageOrientation) {
            
        case UIImageOrientationDown:
            
        case UIImageOrientationDownMirrored:
            
            transform = CGAffineTransformTranslate(transform, aImage.size.width, aImage.size.height);
            
            transform = CGAffineTransformRotate(transform, M_PI);
            
            break;
            
        
        case UIImageOrientationLeft:
            
        case UIImageOrientationLeftMirrored:
            
            transform = CGAffineTransformTranslate(transform, aImage.size.width, 0);
            
            transform = CGAffineTransformRotate(transform, M_PI_2);
            
            break;
            
            
            
        case UIImageOrientationRight:
            
        case UIImageOrientationRightMirrored:
            
            transform = CGAffineTransformTranslate(transform, 0, aImage.size.height);
            
            transform = CGAffineTransformRotate(transform, -M_PI_2);
            
            break;
            
        default:
            
            break;
            
    }

    switch (aImage.imageOrientation) {
            
        case UIImageOrientationUpMirrored:
            
        case UIImageOrientationDownMirrored:
            
            transform = CGAffineTransformTranslate(transform, aImage.size.width, 0);
            
            transform = CGAffineTransformScale(transform, -1, 1);
            
            break;
        
        case UIImageOrientationLeftMirrored:
            
        case UIImageOrientationRightMirrored:
            
            transform = CGAffineTransformTranslate(transform, aImage.size.height, 0);
            
            transform = CGAffineTransformScale(transform, -1, 1);
            
            break;
            
        default:
            
            break;
            
    }
    
    CGContextRef ctx = CGBitmapContextCreate(NULL, aImage.size.width, aImage.size.height,
                                             
                                             CGImageGetBitsPerComponent(aImage.CGImage), 0,
                                             
                                             CGImageGetColorSpace(aImage.CGImage),
                                             
                                             CGImageGetBitmapInfo(aImage.CGImage));
    
    CGContextConcatCTM(ctx, transform);
    
    switch (aImage.imageOrientation) {
            
        case UIImageOrientationLeft:
            
        case UIImageOrientationLeftMirrored:
            
        case UIImageOrientationRight:
            
        case UIImageOrientationRightMirrored:
            
            // Grr...
            
            CGContextDrawImage(ctx, CGRectMake(0,0,aImage.size.height,aImage.size.width), aImage.CGImage);
            
            break;
        
        default:
            
            CGContextDrawImage(ctx, CGRectMake(0,0,aImage.size.width,aImage.size.height), aImage.CGImage);
            
            break;
            
    }
    // And now we just create a new UIImage from the drawing context
    
    CGImageRef cgimg = CGBitmapContextCreateImage(ctx);
    
    UIImage *img = [UIImage imageWithCGImage:cgimg];
    
    CGContextRelease(ctx);
    
    CGImageRelease(cgimg);
    
    return img;
    
}