IOS, ios9

IOS, ios9

/* ____________________ NSString (immutable string )________________________*/

// ________________________ 1. Create a string ___________________________________//

// Create a String constant

NSString * string1 = @ "Hello"; // The content remains unchanged.

String1 = @ "Hello world ";

// Create a string

NSString * string2 = [[NSString alloc] initWithString: @ "Hello"]; // string2 = hello

NSString * string3 = [[NSString alloc] initWithFormat: @ "Hello % @", string2]; // string3 = hello

NSLog (@ "string2 = % @", string2 );

NSLog (@ "string3 = % @", string3 );

// InitWithFormat can be used to place placeholders (formatting characters ). Splicing function (string, including basic data types)

// Example of initWtihformat usage:

// For example, if a result is queried, all the results are spliced and output.

NSString * s1 = @ "zhangsan ";

NSString * s2 = @ "lisi ";

NSString * s3 = @ "wangwu ";

// Concatenate a string

NSString * string4 = [NSString stringWithFormat: @ "% @, % @, % @", s1, s2, s3];

NSLog (@ "% @", string4 );

// Basic data types can also be spliced (initWithFormat)

Int age = 24;

NSString * string5 = [[NSString alloc] initWithFormat: @ "% @ age: % d", s1, age];

NSLog (@ "string5 =%@", string5 );

// ________________________ 2. Comparison of strings ______________________________________

NSString * string6 = @ "abck ";

NSString * string7 = @" 88888 ";

// Compare whether the two pointer addresses are the same, instead of comparing the content in the string

// If (string6 = string7)

// * Isw.tostring compares whether the content of the two strings is the same. (Case Sensitive)

If ([string6 isw.tostring: string7]) {

NSLog (@ "the same content as string6 and string7 ");

}

NSString * string8 = @ "abc ";

NSString * string9 = @ "abc ";

If (string8 = string9 ){

NSLog (@ "string8 = string9"); // YES

}

// Compare the following

NSString * string10 = [[NSString alloc] initWithFormat: @ "abc % @", @ "def"];

NSString * string11 = [[NSString alloc] initWithFormat: @ "abc % @", @ "def"];

If (string10 = string11 ){

NSLog (@ "string10 = string11"); // NO

}

If ([string10 isdue to: string11]) {

NSLog (@ "string10, the content of string11 is the same"); // YES

}

NSString * string12 = [[NSString alloc] initWithString: @ "abc"];

NSString * string13 = [[NSString alloc] initWithString: @ "abc"];

If (string12 = string13 ){

NSLog (@ "string12 = string13"); // YES reason: iniWithString is not created in the heap, but in the constant area.

}

/*

1. initWithString is not created in the heap, but in the constant area (this is not optimized by the compiler)

2. iniWithFormat: created in the heap.

*/

// __________________ String case-insensitive comparison of caxeInsensitiveCompare ______________

// Compare the size

NSString * string14 = @ "zhangsan ";

NSString * string15 = @ "ZHANGSAN ";

// CaseInsensitiveCompare case-insensitive comparison

// Typedef NS_ENUM (NSInteger, NSComparisonResult) {NSOrderedAscending =-1L, NSOrderedSame, NSOrderedDescending };

//-(NSComparisonResult) caseInsensitiveCompare :( NSString *) string;

NSComparisonResult result = [string14 caseInsensitiveCompare: string15];

If (result = NSOrderedSame ){

NSLog (@ "string14, string15 case insensitive ");

}

NSString * string16 = @ "";

NSString * string17 = @ "B ";

NSComparisonResult result2 = [string16 compare: string17];

If (result2 = NSOrderedAscending ){

NSLog (@ "string16 <string17 ");

} Else if (result2 = NSOrderedSame ){

NSLog (@ "string16 = string17 ");

} Else if (result2 = NSOrderedSame ){

NSLog (@ "string16> string 17 ");

}

// _________________ 3. Other usage of the string ________________

// 3.1 length: obtains the length of a string.

NSString * string18 = @ "abcdef"; // @ "" (Length: 2)

NSInteger len = [string18 length];

NSLog (@ "leng = % ld", len );

// 3.2 rpm, write

NSString * string19 = @ "hElllo ";

// UppercaseString: converts all letters in the string to uppercase.

NSLog (@ "upper: % @", [string19 uppercaseString]);

// Lowercase

NSLog (@ "lower: % @", [string19 lowercaseString]);

// Uppercase letters

NSLog (@ "capitalizedString: % @", [string19 capitalizedString]);

// 3.3 convert string to cost data type

NSString * string20 = @" 3.14 ";

// Error: forced conversion cannot change the object itself

// Float f2 = (float) string20; // error message: Pointer cannot be cast to type 'float'

Float f = [string20 floatValue];

NSLog (@ "floatValue: % f", f );

NSString * string21 = @ "1 ";

Bool B = [string21 boolValue]; // true

NSLog (@ "% I", B );

// Truncate a string of 3.4 (***)

NSString * string22 = @ "abcdef ";

// SubstringToIndex: truncates the string from the start position to the specified position (excluding the character 0 at the specified position ).

NSString * substring1 = [string22 substringToIndex: 3];

NSLog (@ "subtirng1 = % @", substring1 );

// SubstirngFromIndex: truncates a string from a specified position to the end of the string (including characters with a specified position)

NSString * substring2 = [string22 substringFromIndex: 1];

NSLog (@ "subtirng2 =%@", substring2 );

Nsange rang = {1, 4 };

// Nsange rang = NSMakeRange (1, 4); // wait for the rang to be smaller than that of nsange rang = };

NSString * substring3 = [string22 substringWithRange: rang];

NSLog (@ "sustirng3 = % @", substring3 );

// Append the 3.5 string

NSString * string23 = @ "Android ";

// Append @ "ios" to the string string23"

NSString * string24 = [string23 stringByAppendingString: @ "ios"];

NSLog (@ "string24 =%@", string24 );

NSString * string25 = [string23 stringByAppendingFormat: @ "% @ % d", @ "ios", 7];

NSLog (@ "string25 = % @", string25 );

// Query rangeOfString for string 3.6

NSString * string26 = @ "www.iphonetrain.com/ios.html ";

Nsange rg = [string26 rangeOfString: @ "ios"];

// No string to be searched

// NSNotFound definition: enum {NSNotFound = NSIntegerMax}; # define NSIntegerMax LONG_MAX

If (rg. length! = NSNotFound ){

NSLog (@ "location: % ld, length: % ld", rg. location, rg. length );

}