NSParagraphStyleAttributeName

    NSMutableDictionary *txtDict = [NSMutableDictionary dictionary];
    NSMutableParagraphStyle *aParagraphStyle = [[NSMutableParagraphStyle alloc] init];
    aParagraphStyle.minimumLineHeight = 18;//最低行高
    aParagraphStyle.maximumLineHeight = 18;//最大行高
    [aParagraphStyle setLineBreakMode:NSLineBreakByWordWrapping];
    [txtDict setObject:aParagraphStyle forKey:NSParagraphStyleAttributeName];
    NSAttributedString *placeHolderString = [[NSAttributedString alloc] initWithString:@"xxx" attributes:txtDict]

//   NSParagraphStyleAttributeName 段落的风格（设置首行，行间距，对齐方式什么的）看自己需要什么属性，写什么    
    NSMutableParagraphStyle *paragraphStyle = [[NSMutableParagraphStyle alloc] init];    
    paragraphStyle.lineSpacing = 10;// 字体的行间距    
    paragraphStyle.firstLineHeadIndent = 20.0f;//首行缩进    
    paragraphStyle.alignment = NSTextAlignmentJustified;//（两端对齐的）文本对齐方式：（左，中，右，两端对齐，自然）    
    paragraphStyle.lineBreakMode = NSLineBreakByTruncatingTail;//结尾部分的内容以……方式省略 ( "...wxyz" ,"abcd..." ,"ab...yz")    
    paragraphStyle.headIndent = 20;//整体缩进(首行除外)    
    paragraphStyle.tailIndent = 20;//    
    paragraphStyle.minimumLineHeight = 10;//最低行高    
    paragraphStyle.maximumLineHeight = 20;//最大行高    
    paragraphStyle.paragraphSpacing = 15;//段与段之间的间距    
    paragraphStyle.paragraphSpacingBefore = 22.0f;//段首行空白空间/* Distance between the bottom of the previous paragraph (or the end of its paragraphSpacing, if any) and the top of this paragraph. */    
    paragraphStyle.baseWritingDirection = NSWritingDirectionLeftToRight;//从左到右的书写方向（一共➡️三种）    
    paragraphStyle.lineHeightMultiple = 15;/* Natural line height is multiplied by this factor (if positive) before being constrained by minimum and maximum line height. */    
    paragraphStyle.hyphenationFactor = 1;//连字属性 在iOS，唯一支持的值分别为0和1