iOS：Objective-C字面量

来源：互联网发布：内蒙古大数据编辑：程序博客网时间：2024/05/21 09:34

http://blog.csdn.net/annkie/article/details/9722659

Objective-c早就支持字面量，但是iOS到XCODE 4.5，IOS6，LLVM4.0才开始较好的支持字面量。

以下是简要对比：

未使用字面量

使用字面量

NSString *greeting = [NSString stringWithUTF8String:"Hello World"];NSString *greeting = @"Hello World";NSNumber *number;NSNumber *number;number = [NSNumber numberWithChar:'X'];number = @'X';number = [NSNumber numberWithInt:12345];number = @12345;number = [NSNumber numberWithUnsignedLong:12345ul];number = @12345ul;number = [NSNumber numberWithLongLong:12345ll];number = @12345ll;number = [NSNumber numberWithFloat:123.45f];number = @123.45f;number = [NSNumber numberWithDouble:123.45];number = @123.45;number = [NSNumber numberWithBool:YES];number = @YES;[NSNumber numberWithint:6 + x * 2012]@(6+x*2012)NSNumber *piOverSixteen = [NSNumber numberWithDouble: (M_PI / 16)];NSNumber *piOverSixteen = @( M_PI / 16 );NSNumber *hexDigit = [NSNumber numberWithChar:"0123456789ABCDEF"[i % 16]];NSNumber *hexDigit = @( "0123456789ABCDEF"[i % 16] );NSNumber *hexDigit = @( "0123456789ABCDEF"[i % 16] );NSNumber *usesScreenFonts = [NSNumber numberWithBool:[NSLayoutManager usesScreenFonts]];NSNumber *usesScreenFonts = @( [NSLayoutManager usesScreenFonts] );NSNumber *writingDirection = [NSNumber numberWithInt:NSWritingDirectionLeftToRight];NSNumber *writingDirection = @( NSWritingDirectionLeftToRight );NSNumber *path = [NSString stringWithUTF8String: getenv("PATH")];NSNumber *path = @( getenv("PATH") );array = [NSArray arrayWithObjects:a, b, c, nil];array = @[ a, b, c ];[array objectAtIndex:1]array[1]dict = [NSDictionary dictionaryWithObjects:@[o1, o2, o3] forKeys:@[k1, k2, k3]];dict = @{ k1 : o1, k2 : o2, k3 : o3 };[NSDictionary dictionaryWithObjectsAndKeys: v1, k1, v2, k2, nil];@{k1:v1, k2:v2}[dictionary valueForKey:k]dictionary[k]

注：

@YES/@NO和下标功能从IOS6才开始支持（XCODE4.5+LLVM4.0）。

其他字面量从XCODE4.4+LLVM4.0就已经支持。

详情参见：

XCode中Objective-C功能支持情况索引

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