NSPredicate的完全用法
NSPredicate描述查询的方式,原理类似于在数据库中进行查询
计算谓词:
//基本的查询
NSPredicate *predicate;
predicate = [NSPredicate predicateWithFormat: @"name =='Herbie'"];
BOOLmatch = [predicate evaluateWithObject: car];
NSLog(@"%s", (match) ? "YES" : "NO");
//在整个cars里面循环比较
predicate= [NSPredicate predicateWithFormat: @"engine.horsepower> 150"];
NSArray*cars = [garage cars];
for(Car *car in [garage cars]) {
if([predicate evaluateWithObject: car]) {
NSLog(@"%@", car.name);
}
}
//输出完整的信息
predicate= [NSPredicate predicateWithFormat: @"engine.horsepower> 150"];
NSArray*results;
results= [cars filteredArrayUsingPredicate: predicate];
NSLog(@"%@", results);
//含有变量的谓词
NSPredicate*predicateTemplate = [NSPredicate predicateWithFormat:@"name ==$NAME"];
NSDictionary*varDict;
varDict= [NSDictionary dictionaryWithObjectsAndKeys:
@"Herbie",@"NAME", nil];
predicate= [predicateTemplate predicateWithSubstitutionVariables:varDict];
NSLog(@"SNORGLE:%@", predicate);
match= [predicate evaluateWithObject: car];
NSLog (@"%s", (match) ? "YES" :"NO");
//注意不能使用$VARIABLE作为路径名,因为它值代表值
//谓词字符窜还支持c语言中一些常用的运算符
predicate= [NSPredicate predicateWithFormat:
@"(engine.horsepower> 50) AND (engine.horsepower <200)"];
results= [cars filteredArrayUsingPredicate: predicate];
NSLog(@"oop %@", results);
predicate= [NSPredicate predicateWithFormat: @"name <'Newton'"];
results= [cars filteredArrayUsingPredicate: predicate];
NSLog(@"%@", [results valueForKey: @"name"]);
//强大的数组运算符
predicate= [NSPredicate predicateWithFormat:
@"engine.horsepowerBETWEEN { 50, 200 }"];
results= [cars filteredArrayUsingPredicate: predicate];
NSLog(@"%@", results);
NSArray*betweens = [NSArray arrayWithObjects:
[NSNumbernumberWithInt: 50], [NSNumber numberWithInt: 200], nil];
predicate= [NSPredicate predicateWithFormat: @"engine.horsepower BETWEEN%@", betweens];
results= [cars filteredArrayUsingPredicate: predicate];
NSLog(@"%@", results);
predicateTemplate= [NSPredicate predicateWithFormat: @"engine.horsepower BETWEEN$POWERS"];
varDict= [NSDictionary dictionaryWithObjectsAndKeys: betweens, @"POWERS",nil];
predicate= [predicateTemplate predicateWithSubstitutionVariables:varDict];
计算谓词:
//基本的查询
NSPredicate *predicate;
predicate = [NSPredicate predicateWithFormat: @"name =='Herbie'"];
BOOLmatch = [predicate evaluateWithObject: car];
NSLog(@"%s", (match) ? "YES" : "NO");
//在整个cars里面循环比较
predicate= [NSPredicate predicateWithFormat: @"engine.horsepower> 150"];
NSArray*cars = [garage cars];
for(Car *car in [garage cars]) {
if([predicate evaluateWithObject: car]) {
NSLog(@"%@", car.name);
}
}
//输出完整的信息
predicate= [NSPredicate predicateWithFormat: @"engine.horsepower> 150"];
NSArray*results;
results= [cars filteredArrayUsingPredicate: predicate];
NSLog(@"%@", results);
//含有变量的谓词
NSPredicate*predicateTemplate = [NSPredicate predicateWithFormat:@"name ==$NAME"];
NSDictionary*varDict;
varDict= [NSDictionary dictionaryWithObjectsAndKeys:
@"Herbie",@"NAME", nil];
predicate= [predicateTemplate predicateWithSubstitutionVariables:varDict];
NSLog(@"SNORGLE:%@", predicate);
match= [predicate evaluateWithObject: car];
NSLog (@"%s", (match) ? "YES" :"NO");
//注意不能使用$VARIABLE作为路径名,因为它值代表值
//谓词字符窜还支持c语言中一些常用的运算符
predicate= [NSPredicate predicateWithFormat:
@"(engine.horsepower> 50) AND (engine.horsepower <200)"];
results= [cars filteredArrayUsingPredicate: predicate];
NSLog(@"oop %@", results);
predicate= [NSPredicate predicateWithFormat: @"name <'Newton'"];
results= [cars filteredArrayUsingPredicate: predicate];
NSLog(@"%@", [results valueForKey: @"name"]);
//强大的数组运算符
predicate= [NSPredicate predicateWithFormat:
@"engine.horsepowerBETWEEN { 50, 200 }"];
results= [cars filteredArrayUsingPredicate: predicate];
NSLog(@"%@", results);
NSArray*betweens = [NSArray arrayWithObjects:
[NSNumbernumberWithInt: 50], [NSNumber numberWithInt: 200], nil];
predicate= [NSPredicate predicateWithFormat: @"engine.horsepower BETWEEN%@", betweens];
results= [cars filteredArrayUsingPredicate: predicate];
NSLog(@"%@", results);
predicateTemplate= [NSPredicate predicateWithFormat: @"engine.horsepower BETWEEN$POWERS"];
varDict= [NSDictionary dictionaryWithObjectsAndKeys: betweens, @"POWERS",nil];
predicate= [predicateTemplate predicateWithSubstitutionVariables:varDict];
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